Fundamentals of Animal Nutrition 9811591245, 9789811591242

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Subodh Kumar Saha Nitya Nand Pathak

Fundamentals of Animal Nutrition

Fundamentals of Animal Nutrition

Subodh Kumar Saha • Nitya Nand Pathak

Fundamentals of Animal Nutrition

Subodh Kumar Saha Indian Veterinary Research Institute Bareilly, Uttar Pradesh, India

Nitya Nand Pathak National Academy of Veterinary Nutrition and Animal Welfare Bareilly, Uttar Pradesh, India

ISBN 978-981-15-9124-2 ISBN 978-981-15-9125-9 https://doi.org/10.1007/978-981-15-9125-9

(eBook)

# The Editor(s) (if applicable) and The Author(s), under exclusive license to Springer Nature Singapore Pte Ltd. 2021 This work is subject to copyright. All rights are solely and exclusively licensed by the Publisher, whether the whole or part of the material is concerned, specifically the rights of translation, reprinting, reuse of illustrations, recitation, broadcasting, reproduction on microfilms or in any other physical way, and transmission or information storage and retrieval, electronic adaptation, computer software, or by similar or dissimilar methodology now known or hereafter developed. The use of general descriptive names, registered names, trademarks, service marks, etc. in this publication does not imply, even in the absence of a specific statement, that such names are exempt from the relevant protective laws and regulations and therefore free for general use. The publisher, the authors, and the editors are safe to assume that the advice and information in this book are believed to be true and accurate at the date of publication. Neither the publisher nor the authors or the editors give a warranty, expressed or implied, with respect to the material contained herein or for any errors or omissions that may have been made. The publisher remains neutral with regard to jurisdictional claims in published maps and institutional affiliations. This Springer imprint is published by the registered company Springer Nature Singapore Pte Ltd. The registered company address is: 152 Beach Road, #21-01/04 Gateway East, Singapore 189721, Singapore

Preface

Nutrition of animals is vital for livestock production and the sustenance of good and sound health. This is not only a mere science but is an art. The nutrition is the basic need of raw materials in a definite quantity for the optimum and potential production of any biological products and biological synthesis of all the physiological processes. Any deviation from optimum quality of the raw materials causes pathological problems in animals. This book integrates the information about basic needs concerning the nature of nutrients and their digestion, assimilation, and metabolism. The book establishes a basis for selecting foods and compounding diets and ration adequate for the nourishment of man and livestock under specified age, stage of production and reproduction, environments, and conditions. The subject of nutrition is concerned with the nature of foods and nutrients. It is imperative to know the nutritional characteristics of food. We have to know the biological system, too, for its operation as a metabolic machine. Plants are also biological machines built with the same chemicals as animals. For sustenance of the livestock life, it entirely depends on the foods of plants and animals. Therefore, it is sure that the same general scheme is helpful to describe both the animals and their foods. The anatomy, i.e., the physical structure of the animals, is also a factor in its nutrition, and to know some of the events, there is a need to know the mechanical structure of the body. To maintain the physical system, we highly depend on the nutritional requirements. So nutrients are needed not only for livestock production and energy supply but also to maintain its physical integrity and structural sustenance. The instinctive reactions to hunger are present at birth in all animals. At that stage, nutrition is highly concerned with distinguishing food from non-food materials. After birth, the young animals instinctively eat anything they get in access and put into their mouth. For example, during the early life, sawdust was used for the bedding and a separate feeder is used for feeding. Therefore, when they feel hungry, they will, from their hunger instinct, start to search for food, and they begin to feed the sawdust as it in front of them. So it is due to the instinct for eating, selection of food is not there. Therefore, for guiding them to feed the food, the sawdust is removed from there, replacing the feed so that the only material they will eat is feed. They will taste better from feed and make a habit of going to the feeder where feed is available. Here we have to establish the learning by experience though it is v

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slow; however, one of the objectives of the art of nutrition is the direction of food selection and to make it a regular habit in the animal. Darwin opined that instincts are changeable by the elimination through the selection of those that are not successful in surviving the species, coupled with the hereditary continuance of course with genetic modification, of those that help the animals adapt to a changing climate. This book consists of seventeen chapters that provide essential information for graduate and postgraduate students. It also caters to researchers and policymakers. During the manuscript preparation, we received support from our family members, friends, colleagues, and co-workers for which we are highly indebted. My wife Sutapa, son Akash, and daughter Shreyashi who continuously extended their support and helped complete this book are highly acknowledged. My daughter Shreyashi, who has given her artworks in the book and has also checked my manuscripts many times, is greatly acknowledged. The help extended during the preparation of the manuscript by all the family members, sons, daughters, grandson, granddaughters, sons-in-law, and daughters-in-law especially Priya Bhasini, Sanjay, Rahul (Prof. Pathak’s daughter, son-in-law, and grandson) is also whole-heartedly acknowledged. We also acknowledge the help and support provided by the publisher, Springer Nature. Last but not least, we thank all those who directly and indirectly supported and helped us for the successful publication of this book. Bareilly, Uttar Pradesh, India Hisar, India

Subodh Kumar Saha Nitya Nand Pathak

Introduction

It is a well-established fact that life is not possible without proper nutrition. The nutrition is very important and primary basic needs to sustain the life. Without proper nutrition, every vital physiological process like circulation, respiration will be disturbed. Not only nutrition to the animal, it is also important to maintain the biological system by supplying necessary demands of the vital nutrients for making the life happy, comfortable and healthy. The healthy and happy life then will further proceed for good activities, produce and reproduce. In animal nutrition, balanced nutrition is the ration where we should provide all the necessary nutrients such as energy, protein, lipids, vitamins, minerals and others through ration or diet for 24 h for a particular purpose, i.e. maintenance, growth, reproduction, lactation, works for an animal. Foods are the main sources of nutrients, and balancing of diet requires variety of supplements. Main sources of nutrients on the earth are variety of herbages. The herbages are equipped with the physio-physiological processes for deriving different kinds of elements and simple compounds like water and air (oxygen, carbon dioxide and nitrogen). These simple chemicals are processed in the tissues of green herbages for the synthesis of complex organic compounds like amino acids, proteins, carbohydrates, lipids and vitamins. Minerals are entered with water from the soil to plants and herbages. These herbages and their products like flowers, fruits and seeds are the foods of different species of herbivorous animals. The animals are herbivorous, omnivorous and carnivorous. Thus, nutrients move in the cycle of air, water, earth, plants and animals. The mechanism of food synthesis, extractions of nutrients from foods and their digestion and metabolism for the physiological and physical functions of the animals and humans constitute fundamental nutrition. The nutrition of animals is mostly completed by the two principal nutrition cycles. The first nutrition cycle is completed in the living plants. In this cycle, elements and inorganic compounds and utilizing solar energy are converted into complex compounds like carbohydrates, proteins, lipids, vitamins, enzymes and hormones. These plant compounds together are the sources of food and nutrients for the animals. The series of processes involved in the transfer of nutrients from the plants to animals and thereafter their utilization for various physiological functions of the animals. A brief history of evolution of the fundamental aspects of nutrition is important for the linkage of progressive development of nutrition and subsequently its branching into human nutrition, animal nutrition, avian nutrition and fish nutrition vii

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among the vertebrates. All living creatures are made up of 4 primary elements that are carbon, nitrogen, hydrogen and oxygen. These four elements and their simple compounds, viz. carbon dioxide, water and nitrogen are the constituents of various compounds forming the body of animals. These compounds are very important and major and essential necessity for living creatures and these are carbohydrate, protein and lipid. The skeletal system is made up of minerals, mainly calcium, phosphorus and magnesium. Some other minerals like iron, copper, zinc, cobalt, manganese and fluorine in traces are essential for many vital functions in the body. The trace elements constitute less than 0.5% of the body but deficiency of any nutritionally important trace element produces harmful clinico-pathological changes in the normal physiological functions. Normal respiration is not possible in the absence of haemoglobin, and haemoglobin formation in the body requires iron and copper. Despite optimum supply of carbohydrates, proteins, lipids and minerals, deficiency of a vitamin or trace mineral can disturb important physiological functions. Vitamin A in the form of retinol is essential for normal vision, iodine is essential for the synthesis of tri-iodothyronine (T3) and thyroxine (T4) essential for energy metabolism and calcitonin is essential for the maintenance of normal structure of the bones. Herbivorous animals are capable of synthesizing vitamin B12 (Cyanocobalamin) utilizing traces of cobalt in the feed. The deficiency of cobalt in the diets of herbivorous animals disturbs metabolism and it was reported that in spite of feeding cobalt free balanced diet, the cattle fail to grow due to the lack of optimum synthesis of muscles and other tissues of the body. In the digestive system of animal, the feeds are disintegrated by the action of different enzymes and bile salts in acidic, alkaline and neutral medium in different segments of the digestive system. The digestion processes differ among the simple stomach animals and modified digestive system of herbivorous animals. The herbivorous animals particularly the ruminants thoroughly eat large quantity of fibrous herbaceous feeds but do not produce fibrolytic enzymes like cellulases and hemicellulases essential for the digestion of fibrous feeds. Thus, they have been evolved to host different kinds of microorganisms possessing characteristic ability of secreting essential enzymes like cellulases and hemicellulases for the digestion of celluloses and hemicelluloses. The end products of digestion are volatile fatty acids like acetic acid, propionic acid, butyric acid and valeric acid in the descending concentration. These acids are the main sources of energy and greater percentage is transported into the body from the pre-abomasal compartments. The herbivorous animals also harbour nitrogen utilizing bacteria for the synthesis of amino acids and proteins. These are also bacteria capable of synthesizing sulphur containing amino acids provided sulphur is ingested in the meal. Trace elements are also active principles in certain enzymes and deficiency of such elements precipitates in the metabolic disturbances showing characteristic pathological and clinical symptoms. Occurrence of goitre on the feeding of iodine deficient diet for longer period of feeding of goitrogenic feeds like mustard-rape forage and subabul (Leucaena leucocephala) for long duration results in the occurrence of goitre and disturbances in metabolism processes in the body. Contamination of animal feeds and forages particularly on the natural grasslands is frequently observed. Such contamination is more common in the hot humid tropical zones.

Introduction

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These contaminants are harmful herbages containing antinutritional and toxic factors. Dry roughages like straws, stovers and hay are satisfactory media for the growth of different species of microorganisms particularly the moulds of hot humid climate. Among these Fusarium sp, Claviceps are quite harmful as they have been isolated from the herbivorous animals feeding on contaminated feeds like paddy straw, sorghum straw, pearl millet stover, etc. The vast subject of fundamental nutrition has been embodied in 17 chapters. Introduction of the subject and brief history of nutrition underlining the important discoveries are followed by the relationship among soil, water, air, solar energy, plants and animals. These provide nutrients for the formation of chemicals and chemical reactions of life in the animal body. Different kinds of herbages are the foods of herbivorous animals, whereas some amount of animal flesh is also eaten by the omnivorous animals. Carnivorous animals eat very small quantity of herbages for the supply of fibre required for the maintenance of peristaltic movements of the alimentary tract. In addition, herbages also supply carotenes and other vitamins. Chemical partitioning of feeds in proximate principles and detergent fibres provide the values of various nutrients in different kinds of feeds. These information are required for the identification and selection of feed ingredients for the formulation of balanced rations for feeding during different stages of life, viz. growth, reproduction in both sexes, lactation and nursing in females and other functions for which animals are trained by the humans. The feeds are then partitioned into water, carbohydrates, lipids, proteins, minerals and vitamins. The other constituents of feed playing important roles in digestion and metabolism in animals by the help of the enzymes and hormones. Some natural sources of feeds also contain one or more kinds of harmful factors. Such feeds require elimination or processing for the destruction or elimination of harmful factors. This has been presented in Chap. 14. The transportation of nutrients from feeds into the body requires chemical disintegration of feeds into appropriate chemical form and size for passage through the wall of the gastrointestinal tract into the body compartments responsible for the transportation and assimilation in the body. The digested foods are transported by absorption, diffusion and pinocytosis. Various feeds are having many toxicant and also to make easily digestible, various processing technologies are available and lots of work are there which are collectively discussed in the book. Therapeutic nutrition is very much important for feeding to sick animals. The clinically ailing animal needs special attention and care. The first and foremost caring is the feeding management. The ailing animals feed depends on the nature of the disease of the animal sufferings. There should be different feed preparation for the different diseases. The feed for animal suffering from digestive problem will be obviously different from the animal suffering from some infectious diseases. The book fundamental of animal nutrition has been written for the researcher, undergraduate and postgraduate students. It has been written as per the necessary of the course of undergraduate and postgraduate students. The book has been compiled in the 17 important chapters and most of the topics are discussed thoroughly and elaborately as far as possible.

Contents

1

Brief History of Animal Nutrition . . . . . . . . . . . . . . . . . . . . . . . . . 1.1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1.2 Animal Nutrition Works in the World . . . . . . . . . . . . . . . . . . 1.3 Animal Nutrition Research in India . . . . . . . . . . . . . . . . . . . References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

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1 1 2 4 6

2

Relationship of Soil, Water, Air, Solar Energy, Plant and Animals . . 2.1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2.2 Soil as Source of Nutrients . . . . . . . . . . . . . . . . . . . . . . . . . . . 2.3 Water as a Source of Nutrients . . . . . . . . . . . . . . . . . . . . . . . . 2.4 Air as Source of Nutrition . . . . . . . . . . . . . . . . . . . . . . . . . . . 2.5 Solar Energy as a Source of Nutrients . . . . . . . . . . . . . . . . . . . 2.6 Factors Affecting Nutritional Composition of Soil . . . . . . . . . . 2.7 Natural Factors Affecting Soil Composition . . . . . . . . . . . . . . 2.8 Role of Microorganisms on Soil Composition . . . . . . . . . . . . . 2.9 Role of Earthworms and Insects on Soil Composition . . . . . . . 2.9.1 Induced Factors Affecting Soil Composition . . . . . . . 2.9.2 Harmful Effects of Insecticides and Pesticides . . . . .

7 7 7 8 8 8 9 9 10 10 10 11

3

Chemicals of Life and Chemical Reactions in the Animal Cells . . . 3.1 The Chemicals of Life . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3.2 Chemical Composition of Animal Body . . . . . . . . . . . . . . . . 3.3 Acids and Bases . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3.4 Salts . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3.5 Elements Required for Body Formation of Animals . . . . . . . . 3.6 Chemical Reactions in Living Cells . . . . . . . . . . . . . . . . . . . 3.7 Reasons for the Occurrence of Metabolism in Small Steps . . . 3.8 Types of Chemical Reactions in Cells . . . . . . . . . . . . . . . . . . 3.9 Nutritional Significance . . . . . . . . . . . . . . . . . . . . . . . . . . . .

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13 13 14 14 16 17 17 18 18 19

4

Partitioning of Foods . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4.1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4.2 Proximate Principles . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4.3 Analysis of the Food . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4.4 Limitations of Proximate Analysis . . . . . . . . . . . . . . . . . . . .

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21 21 21 22 23 xi

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4.5 4.6

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23 23 24 24 25 26

Water . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5.1 Water is an Indispensible Chemical of Life . . . . . . . . . . . . . . . 5.2 Properties of Water . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5.3 Water Properties of Biological Importance . . . . . . . . . . . . . . . 5.4 Functions of Water in Animal Body . . . . . . . . . . . . . . . . . . . . 5.5 Mechanism of Body Temperature Regulation by Body Water . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5.6 Water Absorption . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5.7 Metabolic Water . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5.8 Body (Tissues) Water . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5.9 Factors Affecting Water Content of Body . . . . . . . . . . . . . . . . 5.10 Distribution of Body Water . . . . . . . . . . . . . . . . . . . . . . . . . . 5.10.1 Body Water Compartments . . . . . . . . . . . . . . . . . . . 5.10.2 Water Movement Amongst Body Fluid Compartments . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5.10.3 Methods of Measuring Body Fluid Volume . . . . . . . 5.11 Properties of Marker . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5.12 Some Common Markers Used . . . . . . . . . . . . . . . . . . . . . . . . 5.13 Water Turn Over . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5.14 Water Balance or Water Intake and Out Put . . . . . . . . . . . . . . 5.15 Thirst and Water Intake . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5.16 Sources of Compartmental Water . . . . . . . . . . . . . . . . . . . . . . 5.17 Sources of Drinking Water . . . . . . . . . . . . . . . . . . . . . . . . . . . 5.18 Factors Affecting Water Requirement and Water Intake . . . . . . 5.19 Average Drinking Water Requirement of Different Classes of Farm Animals . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5.20 Uses of Water in Nutrition and Feeding . . . . . . . . . . . . . . . . . 5.21 Quality of Common Drinking Water . . . . . . . . . . . . . . . . . . . . 5.22 Need of Maintaining Water Quality . . . . . . . . . . . . . . . . . . . .

29 29 29 30 31

4.7 4.8 4.9 5

6

Constituents of the Proximate Principles . . . . . . . . . . . . . . . . Uses of Weende Method . . . . . . . . . . . . . . . . . . . . . . . . . . . 4.6.1 Quantity of Samples for Proximate Analysis . . . . . . Precautions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Crude Protein . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Cell Wall Fractions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Carbohydrates . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6.1 Production of Natural Carbohydrates . . . . . . . . . . . . . . . . . . 6.2 Distribution of Carbohydrates . . . . . . . . . . . . . . . . . . . . . . . 6.3 Significance of Carbohydrates in the Diets . . . . . . . . . . . . . . 6.4 Importance of Carbohydrates for Physiological (Vital) Functions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6.5 Classification of Carbohydrates . . . . . . . . . . . . . . . . . . . . . . 6.6 Classification of Carbohydrates on the Basis of End Products .

32 32 33 33 33 34 34 35 35 35 35 35 36 36 36 36 37 37 38 38 38

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39 40 40 40

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41 42 45

Contents

6.7 6.8 6.9 6.10 6.11 6.12 6.13 6.14 6.15 7

xiii

Monosaccharides or Simple Sugars . . . . . . . . . . . . . . . . . . . Structures of Some Important Monosaccharides . . . . . . . . . . Hexoses . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Derivatives of Monosaccharides . . . . . . . . . . . . . . . . . . . . . . Oligosaccharides . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Disaccharides . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Homoglycans . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Heteroglycans . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Fibre in Human Diets . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

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Proteins and Other Nitrogenous Substances of Nutritional Significance . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7.1 Nomenclature of Protein . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7.2 Constituents (Elements of Proteins) . . . . . . . . . . . . . . . . . . . . 7.3 Main Functions of Proteins . . . . . . . . . . . . . . . . . . . . . . . . . . 7.4 Limitations of Average Nitrogen Content in Intact Natural Proteins . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7.5 True Protein Vis-à-Vis Crude Protein . . . . . . . . . . . . . . . . . . . 7.6 Structure of Proteins . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7.7 Classification of Proteins on the Basis of Chemical and Structural Forms . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7.8 Classificiation of proteins on the basis of physiological and nutritional roles . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7.9 Classification of Proteins for the Nutrition of Ruminants and Other Herbivorous Animals . . . . . . . . . . . . . . . . . . . . . . . 7.10 Non-Protein Nitrogenous (NPN) Compounds as Sources of Protein Supply in Ruminants and Pseudoruminants . . . . . . . 7.11 Other Nitrogenous Compounds in the Body . . . . . . . . . . . . . . 7.12 Molecular Weight and Number of Amino Acids in Some Protein Molecules . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7.13 Amino Acids Composition of Proteins . . . . . . . . . . . . . . . . . . 7.14 Amino Acids . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7.14.1 Amino Acids of Animals and Plants Tissues . . . . . . . 7.14.2 Identification of Amino Acids . . . . . . . . . . . . . . . . . 7.14.3 Normal, Primary or Standard Amino Acids . . . . . . . 7.14.4 Classification of Amino Acids of Natural Proteins on Chemical Characteristics . . . . . . . . . . . . . . . . . . 7.14.5 Properties of Amino Acids . . . . . . . . . . . . . . . . . . . 7.15 Chemical Structures and Compensatory Properties of Amino Acids in Animal Nutrition . . . . . . . . . . . . . . . . . . . . . . . . . . . 7.16 Utilization of Amino Acids (Proteins) in the Body of Animals . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7.17 Glucogenic and Ketogenic Amino Acids . . . . . . . . . . . . . . . . . 7.18 Complete and Incomplete Proteins . . . . . . . . . . . . . . . . . . . . .

45 45 48 50 53 53 56 61 63 65 65 66 66 66 67 68 69 72 73 74 74 80 80 82 82 82 83 84 87 90 90 91 91

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7.19 7.20 8

9

Need of Complete Protein Supplementation in the Diets of True Vegetarian People . . . . . . . . . . . . . . . . . . . . . . . . . . . Non-Protein Nitrogen (NPN) Sources for Protein Supply of Ruminants . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Lipids . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8.1 Functions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8.2 Classification of Lipids . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8.2.1 Classification of Lipids on the Basis of Glycerol and Non-glycerol Lipid Compounds . . . . . . . . . . . 8.2.2 Lipids Classification on the Basis of Saponification . 8.2.3 Lipids Classfication on the Basis of their Main Sources . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8.3 Properties of Simple (Neutral) Fats . . . . . . . . . . . . . . . . . . . . 8.4 Controlled Use of Hydrolysis and Oxidation of Milk (Coagulan/Curd) for Cheese Production . . . . . . . . . . . . . . . . 8.5 Antioxidants . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8.6 Animal Fats . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8.7 Waxes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8.8 Properties of Waxes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8.9 Some Natural Waxes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8.10 Compound Lipids . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8.11 Properties of Phosphoglycerides . . . . . . . . . . . . . . . . . . . . . . 8.12 Derived Lipids or Non-saponifiable Lipids . . . . . . . . . . . . . . 8.13 Properties of Cholesterols . . . . . . . . . . . . . . . . . . . . . . . . . . 8.14 Functions of Cholesterols . . . . . . . . . . . . . . . . . . . . . . . . . . 8.15 Physiological Functions of Prostaglandins . . . . . . . . . . . . . . .

92 92

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93 93 94

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94 95

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95 99

. . . . . . . . . . . .

102 103 103 103 104 104 105 106 107 109 109 110

Mineral Nutrition . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9.1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9.2 Minerals in the Animal Body Tissues . . . . . . . . . . . . . . . . . . . 9.3 Essential Minerals of Nutritional Significance . . . . . . . . . . . . . 9.4 Essential Mineral that Turn Toxic . . . . . . . . . . . . . . . . . . . . . . 9.5 Non-essential Elements in Common Foods/Feeds and Drinking Water . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9.6 Average Content of Essential Minerals in the Body of Animals . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9.7 General Functions of Essential Minerals . . . . . . . . . . . . . . . . . 9.8 Harmful and Toxic Minerals . . . . . . . . . . . . . . . . . . . . . . . . . 9.9 Minerals as Constituents of Amino Acids . . . . . . . . . . . . . . . . 9.10 Mineral as Component of Lipids . . . . . . . . . . . . . . . . . . . . . . 9.11 Minerals in Vitamins . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9.12 Minerals Involved in Enzymes Functions . . . . . . . . . . . . . . . . 9.13 Soil–Water–Plant–Animal Relationship in Mineral Nutrition . .

113 113 114 114 115 115 115 116 117 117 117 118 118 118

Contents

9.14 9.15 9.16 9.17

xv

Area Specific Problems of Mineral Nutrition in India . . . . . . . Sources of Dietary Essential Minerals for the Animals . . . . . . Major Minerals . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Trace Elements . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

. . . .

120 121 122 127

10

Vitamins . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10.1 Nomenclature of Vitamins . . . . . . . . . . . . . . . . . . . . . . . . . . 10.2 Extraordinary Nutrients Prior to Discovery of Vitamins . . . . . 10.3 Division of Fat Soluble and Water Soluble Vitamins . . . . . . . 10.4 Classification of Vitamins . . . . . . . . . . . . . . . . . . . . . . . . . . 10.5 Fat Soluble Vitamins . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10.5.1 Precursors of Vitamin Provitamins . . . . . . . . . . . . . 10.5.2 Vitamin A . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10.5.3 Vitamin D . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10.5.4 Vitamin E . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10.5.5 Vitamin K . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10.5.6 Assay and Units of Fat Soluble Vitamins . . . . . . . . 10.6 Water Soluble Vitamins . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10.6.1 Vitamin B1 (Thiamine) . . . . . . . . . . . . . . . . . . . . . 10.6.2 Riboflavin (Vitamin B2) . . . . . . . . . . . . . . . . . . . . 10.6.3 Niacin . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10.6.4 Vitamin B6 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10.6.5 Pantothenic Acid . . . . . . . . . . . . . . . . . . . . . . . . . 10.6.6 Biotin . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10.6.7 Choline . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10.6.8 Folacin . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10.6.9 Vitamin B12 (Cyanocobalamin) . . . . . . . . . . . . . . . 10.6.10 Vitamin C (Ascorbic Acid) . . . . . . . . . . . . . . . . . .

. . . . . . . . . . . . . . . . . . . . . . .

133 134 135 135 135 135 137 137 144 148 151 154 154 155 157 159 162 164 166 168 169 171 174

11

Enzymes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11.1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11.2 History of Discovery of Enzymes . . . . . . . . . . . . . . . . . . . . . . 11.3 Nature of Enzymes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11.4 Properties of Enzymes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11.5 Co-factors . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11.6 Co-enzymes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11.7 Classification of Enzymes . . . . . . . . . . . . . . . . . . . . . . . . . . . 11.7.1 The Oxidoreductase Enzymes . . . . . . . . . . . . . . . . . 11.7.2 The Transferases . . . . . . . . . . . . . . . . . . . . . . . . . . 11.7.3 The Hydrolases . . . . . . . . . . . . . . . . . . . . . . . . . . . 11.7.4 The Lyases . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11.7.5 The Isomerases . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11.7.6 The Ligases . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11.8 Specific Characteristics of Enzymes . . . . . . . . . . . . . . . . . . . . 11.9 Types of Enzyme Specificity . . . . . . . . . . . . . . . . . . . . . . . . .

177 177 177 178 178 179 179 179 182 183 183 184 184 184 185 185

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Contents

11.10 11.11 11.12 12

13

Mechanism of Enzyme Action in Biochemical Reactions . . . . . 185 Factors Influencing Enzyme Activity . . . . . . . . . . . . . . . . . . . 186 Main Enzymes of Digestive System . . . . . . . . . . . . . . . . . . . . 188

Hormones in Nutrition . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12.1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12.2 Storage of Nutrients in the Body . . . . . . . . . . . . . . . . . . . . . 12.3 Hormone(s) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12.4 Functions of Hormones in Nutrients Utilization . . . . . . . . . . . 12.5 Homoeostasis or Homoeokinesis . . . . . . . . . . . . . . . . . . . . . 12.6 Homoeorhesis . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12.7 Endocrine Regulation of Gastrointestinal Functions . . . . . . . . 12.8 Broad Grouping of Gastrointestinal Hormones . . . . . . . . . . . 12.8.1 Gastrin . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12.8.2 Cholecystokinin-Pancreozymin . . . . . . . . . . . . . . . 12.8.3 Secretin . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12.8.4 Glucose Dependent Insulinotropic Polypeptide (GIP) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12.8.5 Vasoactive Internal Polypeptide (VIP) . . . . . . . . . . 12.9 Steroid Hormones of Nutritional Importance . . . . . . . . . . . . . 12.10 Hormones Involved in Metabolism Regulation . . . . . . . . . . . 12.11 Main Hormonal Regulation in Livestock Production . . . . . . . 12.11.1 Hormonal Regulation of Metabolism . . . . . . . . . . . 12.11.2 Hormonal Regulation of Feed Intake . . . . . . . . . . . 12.11.3 Growth Regulating Hormones . . . . . . . . . . . . . . . . 12.12 Role of Sex Hormones in Growth Regulation . . . . . . . . . . . . 12.13 Commercial Uses of Sex Steroids . . . . . . . . . . . . . . . . . . . . . 12.13.1 Hormones Involved in Regulation of Mammogenesis and Lactation (Mammolysis) . . .

. . . . . . . . . . . .

191 191 191 192 192 192 193 193 194 195 196 196

. . . . . . . . . .

197 197 197 198 198 200 201 202 203 203

. 204

Use of Feed Additives on Livestock Production . . . . . . . . . . . . . . . . 13.1 Introductive . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13.2 Mode of Action of Feed Additives . . . . . . . . . . . . . . . . . . . . . 13.2.1 Antibiotics . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13.2.2 Buffers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13.2.3 Arsenicals . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13.2.4 Methane Inhibitors . . . . . . . . . . . . . . . . . . . . . . . . . 13.2.5 Defaunating Agents . . . . . . . . . . . . . . . . . . . . . . . . 13.2.6 Organic Acids . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13.2.7 Drugs . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13.2.8 Hormones . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13.2.9 Enzymes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13.2.10 Antifungal Agents . . . . . . . . . . . . . . . . . . . . . . . . . 13.2.11 Antioxidants . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13.2.12 Pellet Binders . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

205 205 205 206 209 209 209 210 210 211 211 212 212 213 213

Contents

xvii

13.2.13 Flavouring Agents . . . . . . . . . . . . . . . . . . . . . . . . 13.2.14 Pigmentation Compounds . . . . . . . . . . . . . . . . . . . 13.3 Plant Material Affecting Animal Performances . . . . . . . . . . . 13.4 Others . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14

15

. . . . .

214 214 214 215 215

Digestion, Absorption and Metabolism of Nutrients . . . . . . . . . . . . 14.1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14.2 Digestive Enzymes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14.3 Monogastric Animals . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14.3.1 Digestion in the Mouth . . . . . . . . . . . . . . . . . . . . . . 14.3.2 Digestion in the Stomach . . . . . . . . . . . . . . . . . . . . 14.3.3 Digestion in the Small Intestine . . . . . . . . . . . . . . . . 14.3.4 Digestion and Absorbtion in the Large Intestine . . . . 14.3.5 Absorption . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14.4 Metabolism . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14.4.1 Metabolism of Carbohydrates . . . . . . . . . . . . . . . . . 14.5 Glycogenolysis . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14.6 Glycogenesis . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14.7 Pentose Phosphate Pathway . . . . . . . . . . . . . . . . . . . . . . . . . . 14.9 Glucose Regulation by the Hormones . . . . . . . . . . . . . . . . . . . 14.10 Storage of Carbohydrates . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14.11 Metabolism of Protein . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14.12 Deamination and Transamination . . . . . . . . . . . . . . . . . . . . . . 14.12.1 Decarboxylation of Amino Acids . . . . . . . . . . . . . . . 14.13 Biosynthesis of Amino Acids . . . . . . . . . . . . . . . . . . . . . . . . . 14.14 Protein Biosynthesis . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14.15 Essential Amino Acids . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14.16 Fat Metabolism . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14.17 Degradation of Fatty Acids . . . . . . . . . . . . . . . . . . . . . . . . . . 14.18 Ruminants . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14.18.1 Carbohydrate Digestion in the Rumen . . . . . . . . . . . 14.18.2 Protein Digestion . . . . . . . . . . . . . . . . . . . . . . . . . . 14.18.3 Utilization of Non-Protein Nitrogenous Compounds . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14.18.4 Digestion of Fats . . . . . . . . . . . . . . . . . . . . . . . . . . 14.18.5 Digestion of Feed in the Lower Gut . . . . . . . . . . . . . 14.18.6 Absorption . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14.18.7 Rumen Microorganisms . . . . . . . . . . . . . . . . . . . . . References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

219 219 220 221 221 222 222 223 224 224 225 229 230 230 231 231 231 232 233 233 233 233 234 235 235 236 241

Feeding Processes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15.1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15.2 Feeding Processes of Animals . . . . . . . . . . . . . . . . . . . . . . 15.3 Faeces . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

247 247 248 250

. . . .

. . . .

242 243 244 244 244 245

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Contents

15.4 15.5 15.6 15.7 15.8 15.9 15.10 15.11 15.12

Physical Characteristics of Normal Faeces . . . . . . . . . . . . . . Faeces of Animals and Name of Defecations . . . . . . . . . . . . . Cattle . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Bovine Dung . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Equine Dung . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Droppings of Goats and Sheep . . . . . . . . . . . . . . . . . . . . . . . Droppings of Camels . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Droppings of Rabbit . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Excreta of Poultry . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

. . . . . . . . .

250 250 251 251 251 252 252 252 252

16

Energy Partitioning . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16.1 Energy and its Forms According to the Utilization . . . . . . . . . . 16.1.1 Gross Energy/Food Energy . . . . . . . . . . . . . . . . . . . 16.1.2 Digestible Energy . . . . . . . . . . . . . . . . . . . . . . . . . . 16.1.3 Metabolizable Energy . . . . . . . . . . . . . . . . . . . . . . . 16.1.4 Net Energy . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16.1.5 Total Digestible Nutrients (TDN) . . . . . . . . . . . . . . .

253 255 255 255 256 256 258

17

Clinical and Therapeutic Nutrition . . . . . . . . . . . . . . . . . . . . . . . . . 17.1 The Percentage Composition of Animal Body . . . . . . . . . . . . . 17.3.1 Infectious . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17.3.2 Metabolic Disorder . . . . . . . . . . . . . . . . . . . . . . . . . 17.3.3 Physical Problems . . . . . . . . . . . . . . . . . . . . . . . . . 17.3.4 Reproductive Problems . . . . . . . . . . . . . . . . . . . . . . 17.4 Clinical and Therapeutic Nutrition . . . . . . . . . . . . . . . . . . . . . 17.5 Feeding to Sick Animal . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17.6 Principles of Feeding to Sick Animals . . . . . . . . . . . . . . . . . . 17.7 Nutrition and Immunity Interaction . . . . . . . . . . . . . . . . . . . . .

259 260 262 262 263 263 263 264 264 265

Index . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 267

About the Authors

Subodh Kumar Saha, B.V. Sc& A.H., M.Sc. (D), PhD, Post Doctorate (Brisbane-Australia), FNAVS, FNAVNAW, principal Scientist, started his career as a scientist on 1995 at, Central Agricultural Research Institute (CARI), Port Blair, A & N islands. He served as scientist for seven years at CARI. He joined at IVRI, Izatnagar, India in the year 2003 and last 18 years engaged in teaching, research and extension activities at IVRI. He published more than 80 research papers, 150 conference papers and seven books. He has been awarded many prestigious awards and recognitions by different societies and organisation. He visited USA and undergone a training on methane mitigation at Iowa State university, Ames, USA. He was also awarded prestigious Endeavour fellowship award for postdoctoral research in 201516 at CSIRO, Brisbane, Australia. He successfully guided more than 20 post graduate students as an advisor so far. Very recently, he visited Berlin, Germany where he presented an invited lecture. He is the governing council member, NAVS (I) and the general secretary of the Pashu Poshan Kalyan Samiti, Bareilly, India. Nitya Nand Pathak was born on 1st July, at Balia, UP. After his Doctorate, joined in the research service at IVRI. Later on he became head of the Animal Nutrition division on 1990. After few years, he was selected as Director, Central Buffalo Research Institute, Hisar, India. He was the Project Leader of Buffalo Development Project at Song Be in S.R. Vietnam (1982-84). Dr. Pathak worked with more than 150 co-workers. Dr. Pathak published more than 25 books and 350 research papers. He was hold the post as President, Animal Nutrition Association, Izatnagar, India and Animal Nutrition Society of India, Karnal, India. He had been also vice president of Indian Society of Buffalo Development, Hisar and Indian Society of wildlife and Zoo Veterinarians, Bareilly. He was hold the office of general secretary of NAVS (I), New Delhi. He is the founder president of National Academy of Veterinary Nutrition and Animal welfare, Bareilly.

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1

Brief History of Animal Nutrition

1.1

Introduction

The science of food and nutrition in India has its roots in the Vedic period, which is older than the Ramayana and Mahabharat period considered to be more than 5000 years old. Yagya was followed by community feast made up of cooked cereals, roots, tubers, milk and milk products; animal flesh was also the parts of feast at different kinds of festive occasions. During Ramayana and Mahabharat Period hunting of certain species of herbivorous mammals, birds and fishes for food was fully known. The first poem on earth by Valmiki was spontaneously uttered when hunter killed one of the pair of bird engaged in love game. Antelopes, deer, swine and many other species were hunted for food during Ramayana and Mahabharat era. The Imitated golden deer became the cause of abduction of Devi Sita by Ravana in the Kishkindha forest. Animal husbandry and veterinary practice was also well organized in that ancient days. The cattle farming was mainly for milk, milk products and draught power. Horses and elephants were trained for war during these days. Fattened buffaloes for flesh was popular in Lanka during the Ravana period. The science of nutrients production was made commercial during the Maurya period. Acharya Chanakya was instrumental for putting animal husbandry and agriculture for revenue generation. Grasslands and pastures were managed by the state personnel and levy was fixed for grazing animals. Veterinary sciences were free. This system was destroyed by Mugal intruders by burning libraries and dismantling the centres of learning and research. The reminance of ancient knowledge transferred from generation to generation is still found even in remote areas, which is now being revised in the name of Ethno-Veterinary science.

# The Author(s), under exclusive license to Springer Nature Singapore Pte Ltd. 2021 S. K. Saha, N. N. Pathak, Fundamentals of Animal Nutrition, https://doi.org/10.1007/978-981-15-9125-9_1

1

2

1.2

1 Brief History of Animal Nutrition

Animal Nutrition Works in the World

The modern nutrition is claimed to be initiated by Antoine Laurent Lavoisier (1743–1794) who discovered fire, air for burning the substrate. He started experiments with the help of balance and thermometers. The foundation of energy metabolism was laid. He along with Pierre-simon marquis De Laplace fabricated a small respiration calorimeter for Guinea pig. They measured the quantity of carbon dioxide (CO2) expired by Guinea pig in 10 hours. This CO2 was nearly equal to CO2 produced from the burning of 3.33 g carbon. The body heat of same or similar Guinea pig of equal weight melted 3.33 g ice in 10 h. This experiment was the beginning of the use of animal respiration calorimeter for measuring energy metabolism in the animals including humans. It was inferred that the respiration is the source of body heat in living animals and life is a chemical process. Lavoisier was honoured as the father of chemistry and father of nutrition. Thousands of years back it has been clearly stated in ancient Bhartiya literatures that body is made up of chemicals in five main sources, viz. Chhiti (infinite) Jal (Water), Pawak (Fire), Gagan (Sky) and Samira (Air). He reported oxygen in 1778 and hydrogen in 1783 as major components of air. An attempt of determining the fate of the foods ingested (digestion) by Lazzaro Spallanzani (1729–1799), he swallowed weighted small quantity of meat and bread placed in small linen bags tied by thread of long string. He took out bags at predecided intervals and recorded chemical changes at different intervals. This was the beginning of human digestion study. G.J. Muller determined the nitrogen component of foods and protein terminology was coined by Jones Jackob Berzelius in 1838. He reported animals extract had greater proportion of protein than plants. Associate of Muller was Augustus Voelcker (1840). Feeding experiments using semi-purified and purified diets were started by the French François Magendie (1783–1855). In 1816 he stated that source of protein in animals body is the protein in plants eaten. In 1841 he said that value of all protein is not equal for the animals. In later studies M.C. Escher and Roald Hoffmann reported that tyrosine and cystine are absent in gelatin. Justus Von Liebig (1803–1873) postulated that nitrogenous compounds of the herbaceous foods are used for the body building of animals and non-protein parts are utilized for production of body heat. Stephen M. Babcock (1843–1931) developed Babcock method of fat analysis in foods. Nathan Zuntz (1847–1920) started basal metabolism and respiration studies on farm animals. He also fabricated a mobile respiration calorimeter. In 1879 first time clearly claimed fermentation of forage in animals. He also explained in 1891 that rumen bacteria preferably used amides, amino acids and ammonium salts in comparison to protein (Hungate 1966). Wilbur Olin Atwater (1844–1907) constructed respiration calorimeter for human in 1892 in association with E.B. Rosa. He worked out at water physiological fuel value of carbohydrates, protein and fats as 4, 4 and 9, respectively.

1.2 Animal Nutrition Works in the World

3

Oskar Kellner (1851–1911) developed starch equivalent (SE) system of energy estimation in animals. During same period Henry Prentiss Armsby (1851–1921) constructed respiration calorimeter for farm animals and recorded heat production in steers. He developed net energy system of food evaluation. Thomas B. Osborne (1859–1929) and Lafayette B. Mendel (1872–1935) extensively worked on protein and vitamins. Max Rubner (1854–1932) explained that carbohydrates and fats are interchangeable in animal body. Popular books were authored by H.H. Mitchell (1886–1966) entitled comparative Nutrition of Man and Animals, F.B. Morrison (1887–1958) wrote Feeds and Feeding in 1936, which was revised several times. Animal nutrition by Leonard Amby Maynard (1887–1972) became key book of nutrition in many countries. Other authors are Compton, Harris and many others from Europe and America. Maynard’s book was later revised with J.K. Loosli. Max Kleiber (1893–1976) worked out metabolic body size of cattle as body weight W0.75 in place of surface areas for describing energy metabolism. Later on this value has been worked out for different species. Tappliner in 1884 reported that large quantity of volatile fatty acids particularly acetic acid is produced in-vitro from feeds incubated with ruminal bacteria. Extensive studies on microbial digestion and metabolism in rumen were carried out by Barcraft and coworkers during the 1940s. They studied isotope dilution technique. Annison and Lindsay used isotope dilution technique for quantitative measure of VFA production in the rumen of intact animals. Leng R.A. and Ammison (Father in law of Leng) used isotope (C14) for the ketone bodies metabolism in the intact animals. Many scientists, viz. Kurt Nehsing worked on Rostockusitech system of feed evaluation, Tony Joseph Cusha worked on swine nutrition. G.P. Lofgreen used net energy system for feed evaluation. E. J. Underwood extensively worked on minerals metabolism. Ashok Nath Bhattacharya, a non-resident Indian worked on use of poultry droppings for animal feeding. Van Soest developed detergent methods of fibre partitioning in herbaceous fodder (McDonald et al. 1987). A.I. Virtanen was awarded Nobel prize for his pioneer work on replacement of dietary protein by urea nitrogen in the diets of cattle. Virtanen is also known for his novel method of silage making by creating acidic medium of forages. This helped in conservation of greater proportion of organic nutrients by almost complete devoid of fermentation. This was further confirmed by J.T. Reid (1932) who replaced protenous feed from the diets of lactating dairy cow without any adverse effect on the performance.

4

1.3

1 Brief History of Animal Nutrition

Animal Nutrition Research in India

Animal nutrition teaching and research in India (Bharat) started with the establishment of Agriculture college at Loyallpur (now in Pakistan) and establishment of the Laboratory of Physiological Chemist at Pune, IARI, Pusa in Bihar in February 1921. At Layalpur P.E. Lendar and Pandit Lal Chand Dharmani initiated feeding and digestion studies and they also wrote a book on animal nutrition and feeding but Dharmani name was omitted. The laboratory of physiological chemist was shifted from Pusa to Institute of Animals Husbandry and Dairying at Bangalore and shortly it was again shifted at IVRI, Mukteswar in 1935. With in a short time it was brought to IVRI, Izzatnagar during 1937–1938 and finally it was shifted to the present building on March 11, 1939. This building was inaugurated by Victor Alexander John Hope (2nd Marquess of Lord Linlithgow, Fig. 1.1), the then Governor General of India (1936–1943). Accordingly he in the capacity of Chairman, Royal Commission on Agriculture recommended Animal Nutrition Research Institute before 1915 but it didn’t take place due to world war-II (Fig. 1.2 and 1.3). Research work at IVRI was initially oriented for finding the remedy of mutational and metabolic disease of equines (horses, mules and donkeys), dairy animals (cattle and buffaloes) and draft animals (cattle and camel). P.S. Seshan worked extensively on extreme metabolism in cattle, sheep, pony and dogs and he was the first doctor of science (D.Sc.) in 1940. This was followed by a gap of 5 years and S.K. Talapatra who worked on calcium metabolism and B.N. Mazumder on fluorine nutrition were awarded Ph.D. during 1945. Talpatra’s works in wide area in animal nutrition includs oxalate metabolism, method of estimation of calcium in biological material, tripod method of have making in rainfall areas, dietary carotenes for vitamin A activity in poultry and many other animals. At IVRI, Warth was succeeded by Dr. K.C. Sen who used mid Morrison value for using as feeding standard for cattle and buffaloes. Some of two important and major works at A.N. Division, IVRI are the establishment of Respiration Calorimeter for large animals, use of nuclear techniques on animals’ nutrition (later transferred to physiology and climatology division) and laboratory of clinical and pet animal nutrition in 1997. Fig. 1.1 Victor Hope, 2nd Marquess of Linlithgow

1.3 Animal Nutrition Research in India

5

Fig. 1.2 Inauguration programme of the Animal Nutrition Building by his excellency Linglithgow

Fig. 1.3 Animal Nutrition Division, IVRI, Iztnagar inaugurated on March, 1939

6

1 Brief History of Animal Nutrition

During 1950s centres of research in Animals nutrition was spread to Palampur, Anand, Bombay and Meinghata. These were directly attached to animal nutrition division, IVRI, Izatnagar. The scientists incharge of the centre wise were Dr. S.S. Negi, Dr. B.M. Patel, Dr. B.S. Gupta and Sri Mathur. Later on these centres were managed by different institutions. During the same period Dr. Chandra Menon was organising research of animal nutrition and also conducted first digestion study on tamed elephant. Dr. S.K. Talapatra studied the grasses of Assam and awarded D.Sc. In 1950 he joined veterinary college Mathura and guided 50 M.V.Sc. and 10 Ph.D students. Some of the notable animal nutritionists of the country are K.C. Sen, N.D. Kehar, S.N. Ray, D.N. Mullik, S.C. Ray, S.K. Ranjhan and U.B. Singh (Ranjhan 1998). The research work on rumen microorganism was systematically started during later half of the 1950s at the Physiology and Biochemistry Department of Veterinary College, Mathura in the suspension of Prof. Arbind Roy. He was awarded Rafi Ahmad Kidwai award of ICAR in 1961. The laboratory of Rumen Microbiology was established in 1970 in A.N. Division, IVRI, Dr. R.V.N. Srivastava and Dr. S. K. Srivastava initiated work but laboratory gained momentum on the joining of Dr. D. N. Kamra and Dr. Rameswar Singh. Now it is Nutritional Microbiology Laboratory. The animal nutrition at IVRI was organized in laboratories of Animal Nutrition, Mineral nutrition, Vitamin Nutrition, Digestion and Metabolism, Nutritional pathology, Toxicology and plant chemistry and Nutritional biochemistry. Before 1970, many laboratories were upgraded to independent division of Pathology, Physiology and Climatology, Biochemistry and Pharmacology and Toxicology. In research it is a sound practice to specialize on a specified aspect of a subject but in research and teaching a few persons are required to develop expertise in more than one area of the subject. Before 1972 there was no Surgery Division at IVRI. In that time students could not able to work in rumen microbes, if we would have not made rumen and abdominal fistula with cannulation. Animal nutrition is an area and location specific subject. Animal performance is affected by agro-climatic conditions, herbage cover and food resources which are variable. Therefore, there is a need of books composed for the Bhatiya condition. On this aspect few authors to be mentioned are Dr G.C. Banerjee, Dr. S.K. Ranjhan, Dr. U.B. Singh, Dr. N.N. Pathak, Dr. D.N. Kamra and Dr. U.R. Mehra of IVRI, Dr. S.P. Arora and Dr. V. D. Mudgal of NDRI, and Dr. D.V. Reddy of Pondicherry. There is a need of books on the works of Bhartiya universities.

References Hungate RE (1966) The Rumen and its microbes. Academic, New York McDonald P, Edward RA, Greenhalgh JFD (1987) Animal nutrition, 4th edn. Longman Scientific & Technical Group, London Ranjhan SK (1998) Animal nutrition and feeding practices, 6th edn. Vikas Publishing House Pvt. Ltd, New Delhi

2

Relationship of Soil, Water, Air, Solar Energy, Plant and Animals

2.1

Introduction

The survival of animals including humans are depend on the soil, water, air and plants. The animals cannot survive in the absence of any of the four gifts of life. The soil, water, air and sun, are all the four factors provide necessary elements for the synthesis of plant products for the animal use. The plants are the sources of nutrients for the animals, advances and growth for the animals. Advance species of animals derive nutrition from the plants and animals, small quantity is also obtained from the three primary sources. These are soil, water and sunlight (Solar energy).

2.2

Soil as Source of Nutrients

Common soil is made up of several organic and inorganic chemicals. These are present either as elements or different kinds of compounds and mixtures. Organic compounds in soil are the decaying tissue of fallen plants and animals. Degeneration of plants and animals and their mixing in soil is the result of the action of physical, chemical and biological factors. By physical action, the tissue of fallen plants and animals are torn into smaller pieces. These are further disintegrated by the action of water, air, solar radiation and soil microorganisms into chemicals of smaller molecules and also in elements. Distribution of disintegrated products depends on the physical forms (Gaseous products like carbon dioxide (CO2), hydrogen sulphide (H2S), nitrogen in different forms like ammonia and oxides and other gaseous form escape in the environment. Water soluble fraction are dissolved and carried away in the water bodies.

# The Author(s), under exclusive license to Springer Nature Singapore Pte Ltd. 2021 S. K. Saha, N. N. Pathak, Fundamentals of Animal Nutrition, https://doi.org/10.1007/978-981-15-9125-9_2

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8

2.3

2

Relationship of Soil, Water, Air, Solar Energy, Plant and Animals

Water as a Source of Nutrients

Water in the form of H2O (HOH) is a component of carbohydrates. All kinds of carbohydrates contain carbon, hydrogen and oxygen. The latter two are in the ratio of 2:1 in small molecules of carbohydrates, i.e. up to hexoses (C6H12O6). Herbages draw water from the soil moisture and water bodies including irrigation. Water in an essential component of living cells and survival is not possible in the absence of a definite level in the body. This is known as threshold limit and varies with the species and environment. Dehydration tolerance is very high in the animals of arid and semiarid areas. Desert animals are equipped with different anatomical and physiological modification in the body systems for the maintenance of moisture level for vital functions. Water is also transporter of nutrients from the soil to plants and from foods into animal body. Being a good solvent water also dissolves different kinds of harmful substances on flowing through contaminated areas. Water bodies near factories and township are invariably polluted. Use of such water for irrigation contaminates herbages and provides harmful factors (chemicals and pathogens) on drinking. Forages irrigated with contaminated water are often found to contain harmful factors. Such contaminated herbages are found in the areas of industrial effluents. Some harmful factors recorded in contaminated herbages are lead, mercury, arsenic, fluorine, copper, selenium and molybdenum, etc. Many species of plants have been observed to have affinity for harmful substances, viz. rice plant selectively absorbs selenium, the cause of degnala and fluorine responsible for the development of skeletal problems in animals.

2.4

Air as Source of Nutrition

Plants during photosynthesis inspire carbon dioxide (CO2) from the air during day time and utilize it for the synthesis of carbohydrates, proteins, lipids and other organic substances.

2.5

Solar Energy as a Source of Nutrients

Solar radiation is a direct source of calorie for the plants. Chlorophills present in the plants utilize solar energy for the synthesis of organic constituents, viz. carbohydrates, proteins and lipids and oxygen. The very important biochemical process is known as photosynthesis. These organic compounds are stored in different forms and in different parts of the plants. Herbivorous animals normally eat all edible parts of the herbages in the form of whole plant, leaves, roots, stem, inflorescence, fruits and seeds. There is probably no other source of free energy in the form of sunlight for the synthesis of organic constituents of the plants.

2.7 Natural Factors Affecting Soil Composition

9 Sunlight

6CO2 þ 6H2 O þ Chlorophyll ! C6 H12 O6 þ 6O2

2.6

Factors Affecting Nutritional Composition of Soil

Nutrients in different inorganic and organic forms present in the soil are dynamic not only in the cultivated soil but also in Barren lands. Herbages growing on the soil are most important consumers of nutrients in the soil. The other factors affecting the composition of soil are natural and induced.

2.7

Natural Factors Affecting Soil Composition

Flood, wind, landslide and earthquakes are responsible for the change in nutrients composition of soil. 1. Wind is a common factor affecting all kinds of soil on the earth. Loose soil in the form of sand, ash and dust are blown by air from one place and deposited on another place besides spreading variable quantity in route. Quantity of spread and deposition of soil depends on the texture of soil, moisture content in soil and velocity of wind. Changes in soil composition due to wind movement are more in the arid and semi-arid areas. 2. Flood: Effect of the flood is found very limited in the river basins. Flood water dissolve soil and carry from one place to another place. During initial ascending phase of flood velocity of water flow is quite high due to which removal of loose soil is more. During receding of flood velocity of water flow gradually decreases. This favours the formation of silting in the soil and silting of the soil is beneficial and make the soil more fertile. Late sowing is generally common in flood hit areas but harvesting is mostly satisfactory without application of any fertilizer and minimum agricultural operations. However, only limited crops had been found suitable for late sowing on high moisture silts. In most of the river basins main crop is followed by cash crop of cucumbers and similar vegetables. The land of river basins exposed late is used for the cultivation of vegetables, mostly belonging to cucurbitaceae family like bottle gourd, pumpkin, bitter gourd, musk melon, water melon and cucumbers, etc. 3. Landslide: This occurs in hilly areas during the rainy season. It brings virgin soil. The soil flown in streams is carried to rivers and deposited in river basins. The other part deposited in small patches at different strata in hills is leveled and used for farming of food grains, vegetables and seasonal flowers of commercial value. Such situation is common along with entire Himalayan range and also in the areas of coastal hills. Incidence of landslide is quite low in the areas of Vindhyachal and Aravali hills.

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2

Relationship of Soil, Water, Air, Solar Energy, Plant and Animals

4. Earthquake: It happens very rarely in the earthquake zone and more devastating than useful. Indeed earthquake changes the soil composition. These appear to be no specific information on cultivation of crops.

2.8

Role of Microorganisms on Soil Composition

Different species of bacteria, fungi and moulds degrade fibrous substances mixing in soil from herbages and excreta. Substantial quantity of carbon and nitrogenous parts are used for the multiplication of bacteria, fungi and moulds. These are further degraded by interaction. The end product is humus, which is not only the source of nutrients for the plants but also increases water holding capacity of the soil. This moisture maintains continuous supply of nutrients for the growth of herbages.

2.9

Role of Earthworms and Insects on Soil Composition

Several species of earthworms and insects like termite, beetles, multipeds and other insects work for the turnover of soil and degradation of organic wastes added into the soil. The contribution of earthworms and termites in the improvement of soil fertility is well known. These are main players for bringing subsoil on the top level. This action generally improves soil fertility.

2.9.1

Induced Factors Affecting Soil Composition

These are generally area specific, burning of fibrous crop residues, application of silt of seasonal ponds and use of municipal drain water for irrigation are practiced in different parts of the country (Fig. 2.1). 1. Burning of fibrous crop residues: Crop residues and spoiled fibrous residue after the extraction of food grains are burnt in the field itself. This practice is more harmful than beneficial. It causes gaseous pollution. Small benefit of burning is the eradication of weeds and weed seeds to some extent and addition of minerals (ash) in the soil. Harmful insects are also killed but at the same time useful earthworms are also killed. So the soil fertility is in question other than gaseous environmental pollution. 2. Application of Manure- Farm yard manure and municipal manure (now decreasing due to replacement of open toilets by flush toilets) are applied during ploughing of the field for sowing. Animal dropping are composted along with other wastes in pits made in the lands for the purpose in villages. Municipal wastes are composted in trend on Barren land away from the towns and other habitations. 3. Dispersal and mixing of organic dropping in sheep rearing areas it is a common practice of sheep seating in field after the harvesting of crops. In this season

2.9 Role of Earthworms and Insects on Soil Composition

ADDITION OF NUTRIENT IN SOIL

PHYSICAL AND BIOLOGICAL IMPROVEMENT

11

NUTRIENTS IN PLANT

Physical effects - redistribution - soil penetrability - ion movement Biological effects - root distribution - micro-organisms

Fig. 2.1 Physical and biological effects on soil by earthworms

shepherds move with flock for sheep sitting against payment. Sheep are flocked at sun set in the field and moved from one place to another at 3–4 h interval to cover the field up to 8–10 a.m. on next day. During this 12–15 h period sheep spread droppings and urine in the field. Some farmers hire the flock for 24 h. In such cases sheep also graze on residues available in the field consisting of mostly sporadic runners of doob, fallen grains and pods of the harvested crops.

2.9.2

Harmful Effects of Insecticides and Pesticides

Farmers are educated for the benefits of the application of insecticides and pesticides on the crops but generally they are not properly educated for the harmful effects. These pathogens killing chemicals are harmful for also earthworm and other soil turning insects, birds and other animals of beneficial roles. Earthworms renew soil, birds eat harmful insects and their larvae and also rodents. Vegetables produced in such systems are often found harmful for human health. Hence, farmers should be educated for the entire package of practice for reducing the danger to health.

3

Chemicals of Life and Chemical Reactions in the Animal Cells

All constitutional components of a living organism are made up of different kinds of organic and inorganic chemicals. Many of these chemical compounds are also the components of nonliving matters. In the process of exploration of the chemicals of the living bodies and the chemical reactions involved in the synthesis of these chemicals and their functions in the living organism is the science of biochemistry. The cells of tissues are formed of different kinds of molecules and the secretes of life are present in these molecules. The detailed study of these molecules is known as molecular biology. The next step in the development of living cell science which was evolved simultaneously is the bio-engineering. The application of bio-engineering in molecular biology is the biotechnology which is now being used extensively for commercial purpose for the benefits of mankind.

3.1

The Chemicals of Life

Like conventional chemistry, the chemicals of life are formed of two major groups, i.e. organic and inorganic chemicals. All kinds of complex compounds of carbon like carbohydrates, nitrogenous carbonic compounds (amino acids, proteins and enzymes), lipids, hormones and vitamins are the organic chemicals. All other kinds of non-carbon compounds present in the living cells for the maintenance of life are inorganic compounds. The inorganic constituents of living cells and tissue including the body fluids are salts and ions.

# The Author(s), under exclusive license to Springer Nature Singapore Pte Ltd. 2021 S. K. Saha, N. N. Pathak, Fundamentals of Animal Nutrition, https://doi.org/10.1007/978-981-15-9125-9_3

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Chemicals of Life and Chemical Reactions in the Animal Cells

1. Organic compounds: Before 1828 researchers believed that organic compounds are synthesized in the living cells only but this myth was removed on the synthesis of urea, outside the living cell, in the chemical laboratory by the German scientist Friedrich Wohler in 1828. After this discovery, it was clear that organic compounds are not the proprietary of living organisms and can be synthesized in the chemical laboratories from the elements and substances present in the nature. After the synthesis of urea, one of the most important nutritional factors for the global revolution of crop production hundreds of organic compounds have been synthesized and commercialized for use as nutrients, medicines and diagnostics, etc. The organic compounds of the living organisms are the carbohydrates, lipids, nitrogenous organic compounds (proteins, enzymes and nucleic acids) and vitamins. 2. Inorganic compounds: A large number of inorganic elements are found in the form of acids, bases, salts, ions and organic complex compounds like haemoglobin, thyroxine and cofactors in several enzyme systems required for the biochemical reactions of metabolism

3.2

Chemical Composition of Animal Body

There is a large variation in chemical composition of the animal body due to species, age, nutritional supply and other environmental factors. However, in general an animal cell excluding the specialized cells of dermis, cartilage, bones, horns, hooves, hairs and feathers contain about 80% water and 20% solids comprising of organic and inorganic compounds. The solids are 99% organic compounds and less than 1% inorganic compounds in the cells. 1. Organic compounds: The living cells are the nitrogenous organic compounds forming the groups of carbohydrates and lipids, nitrogenous compounds like proteins, enzymes and free amino acids. Some vitamins and hormones contain nitrogen. 2. Inorganic compounds are water, acids, bases and salts. 3. Complex compounds formed of organic and inorganic elements. The medium for reactions is liquid and water (H2O) is the main chemical. Water is responsible for physical activities as a solvent, thermo regulator and excretion.

3.3

Acids and Bases

Water (aqueous medium) is required for the functions of acids and bases in the biological systems. The strength of acid is estimated from its dissociation in the aqueous medium. Hydrochloric acid is a strong acid due to its complete dissociation into hydrogen (H+) and Chlorine (CL
) ions as follows:

3.3 Acids and Bases

15

Aquous medium HCL-----------------------H+ + Cl-

Organic acid like acetic acid is a weak acid because its dissociation in aqueous medium is limited. Only a small percentage of acetic acid (CH3COOH) dissociates into acetate and hydrogen ions. CH3 COOH ! CH3 COOþ The bases are compounds that associate with the hydrogen ion (H+) liberated from the dissociation of acids. The sodium bicarbonate is a base that readily dissociates into sodium (Na+) and bicarbonate (HCO
) ions in an aqueous solution as follows: NaHCO3 ! Naþ þ HCO3
The bicarbonate ion liberated in the reaction is able to combine with the free available hydrogen ion (H+) for formation of carbonic acid (H2CO3) as follows: HCO3
þ Hþ ! H2 CO3
This reaction removes active hydrogen in aqueous solution and reduces acidity. Thus, it is a buffering reaction of sodium bicarbonate. In a condition of increased acidity the bicarbonate reacts with the hydroxyl group (OH
) to produce carbonate ion (CO3
) and water (H2O) as follows: HCO3 þ OH
! CO3
þ H2 O In this way sodium bicarbonate reacts for the maintenance of pH and the ability is called buffering capacity. In the body of most of the common terrestrial mammalian species including the mankind the buffer action of bicarbonates is minor. The main buffering agents are the salts of phosphoric acid (phosphates). The potassium and sodium phosphates work as hydrogen ion (H+) sink responsible for suppressing the hydrogen ion concentration in blood. The phosphate reacts with the free hydrogen ion to produce dihydrogen phosphate as depicted in the following reaction: KHPO4 þ Hþ $ KH2 PO4 þ Kþ Certain organic compounds like proteins and metaloprotein (haemoglobin) are also capable of accepting hydrogen ions and therefore, possess buffering property. This is another important biological role of these compounds. For the proper functioning of living cells and tissues almost neutral medium (marginal deviation is tolerated) pH is required. More than I unit of fluctuation in the pH of biological medium is rarely tolerated by the system. Therefore, it is essential to keep the pH of

16

3

Chemicals of Life and Chemical Reactions in the Animal Cells

body fluid compartments constant to possible extent. Any tendency of increase in acidity of body fluids is counteracted by the buffers which scavenge the excess hydrogen ions and helps in the maintenance of constant environment in the cells and the both media.

3.4

Salts

Some of the mineral salts, compounds of metals with a nonmetal or nonmetallic radical are the most common solutes present in the form of aqueous solution in the body fluids. Sodium chloride is one of the common and important salts of the body fluids. It is known that a salt, when dissolves in the water, dissociates into its constituents ions as follows: NaCl

→

Sodium chloride water

Na + Sodium

+

ClChloride

The salts are ionic compounds and they are decomposed by electricity into free ions which facilitate the passage of electric currents. These salts are called electrolytes. Although, sodium (Na+) and chloride (Cl
) are the important ions of body fluids but several others are also present. The important cations are sodium (Na+), potassium (k+), calcium (Ca++), magnesium (Mg++), copper (Cu++) and iron (Fe++). The important anions are chloride (Cl
), bicarbonate (HCO3
), nitrate (NO3
), phosphate (PO4
), sulphate (SO4
) and iodide (I). In addition to these major ionic minerals some others often present in traces are cobalt (Co++) and molybdenum (usually in MoO4
). These ionic elements and radicals are independent for the animals and plants but few are common for the both. The functions of these minerals salts in the animal body can be summarized as follows: 1. Phosphorus is the constituent of adenosine triphosphate (ATP) and its degraded molecules adenosine diphosphate (ADP) and adenosine monophsophate (AMP). Iodine is a constituent of the thyroid hormone, thyroxine (T3) and tetraiodothyronine (T4). 2. Structural constituents: Proteins forming connective tissue contains phosphorus and sulphur compounds. Nitrogen and phosphorus are the constituents of the nucleic acid (DNA and RNA) present in the chromosomes. Phosphorus is a constituent of cell membrane and in combination with calcium and minute fractions of some other minerals (magnesium forms the skeletal system). 3. Cofactors in the enzymes: Nitrogen is a common constituent of all the enzymes being proteins. Certain enzymes contain a metal ion like copper or iron. For example, catalytic centre of the enzyme catalase is believed to be the iron in the molecule.

3.6 Chemical Reactions in Living Cells

17

4. Metabolic activators: Certain elements are associated with the activation of enzymes. Phosphate is required for the activation of sugar before its disintegration in cell respiration. 5. Constituents of certain pigments: Iron is a constituent of haemoglobin in the animals and chlorophyll of the plants. Iron is also a compound of cytochromes associated with energy release in the cells. 6. Maintenance of anion–cation balance in cells, sodium, potassium and chloride ions are especially important for the normal functions of nerves, muscles and sensory cells involved in the transmission of impulses. 7. Regulator of osmotic pressure: Mineral salts together with other solutes determine the osmotic pressure of the cells and the body fluids. In the mammalian species including humans, the osmotic pressure must not be allowed to fluctuate widely. The physiological functions of the body are designed to prevent undersigned fluctuation in osmotic pressure.

3.5

Elements Required for Body Formation of Animals

The animal body is formed of carbon, hydrogen, oxygen and nitrogen and minerals. The minerals constitute 7 macro or major minerals and about 20 micro minerals comprising of 12 essential and 8 probable essential trace elements. The macro minerals are calcium, phosphorus, magnesium, sodium, potassium, chlorine and sulphur. The trace elements are copper, cobalt, iron, iodine, zinc, fluorine, molybdenum, manganese, selenium, silicon, chromium and boron. The probable trace elements are aluminium, arsenic, bromine, lithium, lead, nickel, tin and vanadium. Some other elements detected in the body of animals are considered due to their presence in the foods of natural and cultivated sources. No role of such elements has been yet found in the body functions.

3.6

Chemical Reactions in Living Cells

The chemical reactions occurring in the living cells are known as metabolism and the molecules produced in the reactions of metabolism are called metabolites. Some of these metabolites are synthesized within the organism and some others are taken in food. Metabolism is a basic characteristic of all living organisms. The metabolic reactions in the body (cells) synthesize compounds for the structural growth and the maintenance of body structure, and release energy for the functions of living organisms. Apparently appearing inactive tissues like bones, cartilage, body and connective tissue also contain living cells involved in metabolic functions. Some of the dead parts of an organ remain attached on the body which are not engaged in metabolic activities. These are hairs (other fibres), nails, horns and hooves of different mammalian species, shells of moluscos and feathers of the avian species. These organs are the continuation of mother live organ but dead and unable to participate in the metabolism. However, these dead tissues remain intact and do not

18

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Chemicals of Life and Chemical Reactions in the Animal Cells

decompose unless they are cut off and thrown on the ground for the action of saprophytic microorganisms normally present in the soil, ground water, air and some herbages, etc. The metabolic reactions occur in small steps instead of one long reaction for the conversion of metabolites into products. A series of reactions take place for the transformation of metabolites into products. These reactions together are known as metabolic pathway. Each step of a metabolic pathway is essential for the complete sequence of reactions for the transformation of raw materials (foods) into products.

3.7

Reasons for the Occurrence of Metabolism in Small Steps

Two important reasons have been identified for the occurrence of metabolism in a series of small steps. 1. Large reactions, especially of a violent nature can endanger the integrity of cell and may kill it. 2. Long metabolic pathways involving several small steps enable the living cells to extract maximum benefit from the reactions. This kind of metabolic reactions are comparable with a careful dismantling of a brick building into undamaged individual bricks so that these bricks can be reused, rather than blowing up of the building breaking the bricks in pieces unfit for use again. For the orderliness of metabolic pathways, a well defined and regulated structural functional organization is required in the cell. Greater part of this organization is achieved by the involvement of enzymes.

3.8

Types of Chemical Reactions in Cells

Two types of chemical reactions occurring in the cells are (1) synthetic or anabolic reactions and (2) breakdown or catabolic reactions. In synthetic reaction molecules are joined together chemically to synthesize more complex compounds. For example, A and B are the substrate molecules for reaction (reactants) which produce AB complex molecule (product). A simple example is the synthesis of one molecule of disaccharide form two molecules of monosaccharide (Fig. 3.1). Synthesis of the disaccharide lactose takes place within the Golgi apparatus of epithelial cells of the lactating mammary gland. The synthesis itself is a single chemical reaction of free glucose and UDP-galactose to form lactose and UDP. Fig. 3.1 Disaccharide lactose

3.9 Nutritional Significance

19

In this example, disaccharide is a product and two molecules of monosaccharide are the substrates. The reverse is true for breakdown products (2 moles of monosaccharide) from the substrate, i.e. one mole of disaccharide. In living cells, anabolism (synthetic reactions) and catabolism (breakdown reactions) are the continuous activities. Anabolic reactions require energy in the form of ATP, and catabolic reactions produce energy. Energy absorbing reactions are called endergonic reactions and energy liberating reactions are known as exergonic reactions. Summary of anabolism and catabolism in a cell after absorption from gut lumen 1. Anabolic reactions are responsible for the synthesis of compounds, building of structures and storage of compounds and complex metabolites in the cell proteins, lipids and carbohydrates are the products of anabolic pathways. Plants and certain bacteria are capable of synthesizing these complex organic molecules from the inorganic elements like carbon, hydrogen, oxygen and nitrogen. Sometimes other elements are also used for the synthesis of special molecules for specific biological function. Animals can synthesize larger or transformed organic molecules from the simple organic molecules, e.g. glycogen from monosaccharide, proteins from amino acids and fats from fatty acids. 2. Catabolic reactions liberate energy for the following three main functions: a. To drive anabolic reactions in the cells for the synthesis of structural and functional compounds. b. For works like contraction of muscles, transmission of nerve impulse, peristaltic movements and secretion of glands. c. For maintenance of almost constant internal environment, and function and heath of tissues and organs. All these functions need energy. Thus, energy is of vital importance for an organism and much of metabolic processes are for the storage and supply of energy in the body.

3.9

Nutritional Significance

It is well known that living organisms are made up of numerous chemical compounds which are mostly complex organic compounds, carbon, hydrogen, oxygen and nitrogen in the form of protein, lipids and carbohydrates (small percentage) constitute all soft tissues and considerable proportion of the hard tissues like bones and cartilages. Minerals, particularly calcium and phosphorus are the major inorganic constituents of skeletal system. Trace elements are essential for the normal physiological functions either as constituents of haemoglobin, myoglobin, thyroid hormones, fibres and connective tissues or as cofactors in enzyme systems. The life processes are carried by well defined chemical compounds and ion through large number of biochemical reactions in the living cells.

4

Partitioning of Foods

4.1

Introduction

The partitioning of feeds is necessary for various purposes. There should be a knowledge regarding content of the feeds and fodder without which one will be ignorant about the nutrition of the animal. Chemical partitioning of feeds in proximate principles and detergent fibres provide the values of various nutrients in different kinds of feeds. These information are required for the identification and selection of feed ingredients for the formulation of balanced rations for feeding during different stages of life, viz. growth, reproduction in both sexes, lactation and nursing in females and other functions for which animals are trained by humans. The requirement of various nutrients is different and the content in the feed also varies greatly. The feeds are then partitioned in water, carbohydrates, lipids, proteins, minerals and vitamins.

4.2

Proximate Principles

The food or feed actually a complex consist of organic and inorganic material, after ingestion by the animal, it is digested into smaller units and it is absorbed for utilization by the body for further biosynthesis of the biomolecules. After ingestion of complex food digested into smaller unit which help for absorption from the intestines. During photosynthesis, plants are able to synthesize complex material from simple substances such as CO2 from the air and water and inorganic materials from the soil in presence of sunlight. The animal and plant consist of the same substances. The common components of food, plants and animal are grouped.

# The Author(s), under exclusive license to Springer Nature Singapore Pte Ltd. 2021 S. K. Saha, N. N. Pathak, Fundamentals of Animal Nutrition, https://doi.org/10.1007/978-981-15-9125-9_4

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22

4

Partitioning of Foods

Food

Water

Dry Maer

ORGANIC

Carbo hydrate

4.3

Protein

Lipid

Nuclic Acid

INORGANIC

Organic Acids

Vitamins

Minerals (Major & minor)

Analysis of the Food

This method was developed for the chemical analysis of feedstuffs, especially the herbages into the related components which were named proximate principles. The method was developed at the Weende Research Station in Germany around 1860 by a team of celebrities like Wilhelm Henneberg (1825–1890) and Friedrich Stohmann (1832–1897). Hence it is also called Weende system of analysis. With the help of this method feeds and other biological materials are partitioned into (1) moisture, (2) crude protein (N X 6.25), (3) ether extract or crude fat, (4) crude fibre, (5) nitrogen free extract and (6) ash or inorganic matters. All constituents are determined by different procedures and the nitrogen free extract is determined by subtraction of the estimated constituents form the initial weight of the sample taken for analysis as follows: NFE ð%Þ ¼ 100  ðCP% þ EE%CF% þ ash% þ moisture%Þ All nitrogenous constituents in the material are determined as total nitrogen (N) and multiplied with 6.25 to determine crude protein (CP). The factor 6.25 has been worked out on the basis of 16% total N in the protein DM of feedstuffs of plant and animals origin with minor variations. However, for milk analysis a factor 6.38 is used as N in milk protein is slightly less. The carbohydrate fractions are comprising of starches and sugars and a less digestible fibre fraction. The fibre fraction is

4.6 Uses of Weende Method

23

determined by boiling a fat free sample, first with a weak acid (representing digestion in stomach in acid medium) and then with weak alkali (representing digestion in intestine in alkaline medium). The insoluble residue thus obtained is called crude fibre. With the passage of time this method has been further elaborated.

4.4

Limitations of Proximate Analysis

1. It does not partition biological materials into well defined chemical constituents. 2. Normally loss of volatile fractions is added in NFE. 3. The assumption about high digestibility of NFE and low digestibility of CF is always not true and reverse is frequently observed. 4. The fibrous fraction lignin is partly dissolved in sodium hydroxide solution and hemicellulose is dissolved by both acid as well as alkali solution. Thus, CF may be under estimated and NFE may be over estimated. 5. Since larger portion of faecal nitrogen is non-protein nitrogen (NPN) and contributed by microbial nitrogen which causes under estimation of faecal CP and over estimation of faecal NFE.

4.5

Constituents of the Proximate Principles

Almost all proximate principles are composed of more than one chemical compound: 1. Water may also include some volatile chemicals when determined by drying in a hot air oven. 2. Ash is formed of minerals and acid insoluble ash or silica. 3. OM includes CP, EE, CF and NFE a. CP includes true protein (TP), amino acids, peptides, purines, nucleic acid, amides, nitrite and nitrates. b. EE contains triglycerides, phospholipids, sterols, waxes, essential oils, fat soluble vitamins and fat soluble pigments like carotenes and xanthophylls. c. CF includes cellulose, major part of hemicelluloses, larger proportion of lignin and cutin. d. NFE contains sugar, starch, glycogen, pectins, fructan and soluble parts of hemicellulose and lignin

4.6

Uses of Weende Method

1. Determination of proximate composition of biological matters.

24

4

Partitioning of Foods

2. Nutritional evaluation of feeds, viz. digestibilities of nutrients, CP%, DCP%, total digestible nutrients (TDN) and starch equivalent (SE) through digestion trials. 3. Comparison of various feeds regarding composition and their digestibility. 4. Identification of unknown feed sample. 5. Acid insoluble ash is used as internal indicator for determining pasture composition and digestibility.

4.6.1

Quantity of Samples for Proximate Analysis

The amount of samples for proximate analysis depends on the density of different components in the material to be analysed. An approximate range for various feedstuffs for different constituents is shown in Table 4.1.

4.7

Precautions

1. All samples except those containing volatile components should be dried at 100  1  C ground to 1–2 mm size and should not contain more than 15% moisture (rarely up to 20%) at storage. 2. Dried materials are ground in a laboratory mill after complete cleaning for each sample. 3. Ground materials should be preserved in clean, dry and covered glass containers or plastic containers or polyethylene bags. All samples must contain number, name, date and other details, if any. 4. Samples should be stored on racks at a dry place protected from rodents and insects. 5. Samples should be weighed either in a clean and dry weighing bottle or stainless scoop. 6. After weighing, the samples are kept either in a desiccators or covered with a bell jar. 7. After quantitative transfer of samples all thimbles should be plugged with non-absorbent cotton wool. Table 4.1 Approximate range of various feedstuffs for different constituents

Feeds Cereal straws Legume straws Cereal grains Cereal brans Pulses (dal) chuni Oil cakes (expeller) Oil cakes (deoiled) Animal protein feeds

DM/ash (g) 8–10 8–10 5–6 5–6 5–6 5–6 5–6 5–6

N (g) 5–6 2–3 2–3 2–3 1–2 0.5–1 0.5–1 1–2

EE/CF (g) 3–5 3–5 3–5 3–5 2–3 2–3 3–5 1–2

4.8 Crude Protein

25

8. Samples in Kjeldahl flasks should be kept at a separate place free from ammonia. Concentrated sulphuric acid should be added for the digestion (wet ashing) in the presence of a mixture of sodium (or potassium), sulphate and copper sulphate in a ratio of 9:1. The mixture is also called digestion mixture. Normally sulphuric acid is added at 10 ml/g sample, but minimum is 25 ml conc. H2SO4. Moisture and Dry matter: The boiling temperature of water is 100  C, and heating of a biological material for a certain time removes total water in the form of water vapour. Normally it takes 10–14 h (overnight) in a hot air oven maintained at 100  1  C or 6–8 h in an oven 60–65  C. DM or moisture in a material is expressed as percentage. However, chemical composition of feeds may be presented on fresh basis (green fodders, silage and haylage) or air dry feeds like straws, hay, grains, oil cakes and brans, etc.) or DM basis. The chemical compositions are preferably presented on DM basis. Total Ash The residue left after complete oxidation/ignition of a biological material is called total ash and represents the inorganic matter contents of the sample. Three to five grams sample is weighed in a previously weighted crucible/basin is heated over a burner or heater to make it smoke free and then placed in a muffle furnace at 550–660  C for 2–3 h for complete ignition. The silica basin with ash is removed from the muffle furnace, cooled in a desiccators to room temperature and weighed to constant weight. The ash may, however, contain organic material, i.e. sulphur and phosphorus from protein and some loss of volatile materials is there in the form of sodium, chloride, potassium, phosphorus and sulphur during ignition. The residue left after boiling total ash with 5N HCl is called acid insoluble ash and it is largely silica.

4.8

Crude Protein

Total nitrogen (N) content is determined with the help of Kjeldahl method. Since average value of N in biological material is 16% on dry matter (DM) basis, a factor 6.25 (100 divided by 16) is used for the determination of CP content. This process of N determination is completed in three steps, viz. digestion of the material for the conversion of nitrogenous compounds into ammonium sulphate, distillation of ammonia in an alkaline medium from the ammonium sulphate and the collection of liberated ammonia into a known volume of standard acid or boric acid and last is the titration of either excess acid by a standard alkali solution or the bound ammonia in boric acid with a standard acid solution. Three types of apparatus are commonly used for the distillation, i.e. macro-Kjeldahl, micro-Kjeldahl and Kjeltek. The last one is automatic and also includes titration and recording. Nitrite and nitrate nitrogen is not determined by kjeldahl method. This is not a true protein since the method estimates the nitrogen other than protein, therefore this fraction is termed as Crude Protein.

26

4

Partitioning of Foods

Table 4.2 The proximate principles of food/feeds Proximate principles Moisture Ash Crude protein Ether extract Crude fibre NFE

Different components Water Essential elements, all the major and minor essential elements Protein, amino acids, amines, nitrates, nitrogenous glycosides, glycolipids, B vitamins, nucleic acids Fats, oil, waxes, organic acids, pigments, sterols, vitamin A, D, E, K Cellulose, hemicelluloses, lignin Cellulose, hemicelluloses, lignin, sugar, fructans, starch, pectins, organic acids, resins, tannins, pigments, water soluble vitamins

Ether Extract Crude fat in biological samples is extracted by refluxing a known quantity of dried or moisture free material with petroleum ether or any other suitable fat solvent. Commonly it is called ether extract (EE) and includes triglycerides, sterols, resins, waxes, essential oils and fat soluble pigments etc. Crude Fibre The digestion of the fat free material present in the thimble with a weak (1.25%) solution of acid followed by a weak (1.25%) solution of alkali in a controlled system for one hour boiling in acis and alkali. The remaining portion is left in the beaker after filtration is CF plus ash. Originally CF was considered to be indigestible fraction but later on it was found digestible. It includes cellulose, some part of hemicelluloses and a major portion of lignin. Nitrogen Free Extract It is calculated amount not estimated. When the sum of the amounts of moisture, ash, crude protein, crude fibre, ether extract is subtracted from 100, the difference is termed as NFE and expressed in g/kg (Table 4.2). The nitrogen free extractives are cellulose, hemicelluloses, lignin, sugar, fructans, starch, pectins, organic acids, resins, tannins, pigments, water soluble vitamins NFE ð%Þ ¼ 100  ðCP% þ EE% þ CF% þ Ash%Þ

4.9

Cell Wall Fractions

As the proximate analysis procedure is highly criticized by the nutritionist and biochemist due to the error in crude fibre estimation and nitrogen free extract calculation, the cell wall analysis system was developed by P.J. Van Soest and R.H. Wine in 1968 and it was based on detergents. The contents of cell wall (Neutral Detergent Fibre: NDF) are determined by extraction of sample in a neutral detergent solution. The residue of sample after extraction in an acid detergent solution is termed as Acid Detergent Fibre (ADF). The lignin may also be analysed. The content of hemicelluloses is a difference between NDF and ADF. The estimation of acid

4.9 Cell Wall Fractions

27

detergent fibre is useful in forages as there is a good correlation between it and digestibility. NDF ¼ Hemicelluloses þ Cellulose þ Lignin ADF ¼ Cellulose þ Lignin Hemicellulose ¼ NDF  ADF It provides a rapid method for lingo-cellulose determination in forages and is also a preparatory step for lignin, cellulose and silica analysis.

5

Water

Water is an essential component of all kinds of life and survival is itake and out putmpossible, if water is lost beyond the critical level. Although in normal course, water is not considered as a nutrient but in expressing chemical composition of organic foods it is one of the important component like other nutrients for any reaction and body metabolism. For correct comparison of chemical composition and nutritive value, estimation of moisture is essential. Standard level of moisture is essential in the body tissues for optimum physiological functions. The significant disturbance or deficiency in water content of body tissues which create an environment for the occurrence of clinic-pathological conditions in the body. Therefore, it is more logical to be included water in the list of nutrients. Water or moisture is already a component of proximate principles.

5.1

Water is an Indispensible Chemical of Life

Water constitutes maximum mass of the human and animal body. More than 80% of most tissues in the body are water and more than 60% water constitutes the body mass of different species. Life is considered to be originated from the water and even today large number of metazoan (animals and plants), protozoa and microorganisms live in the water. The four most principal and important properties of water, viz. solvent nature, heat capacity (or thermal property), surface tension and freezing point have made it most suitable medium for the biochemical processes essential for the maintenance of body functions and its survival.

5.2

Properties of Water

1. Physical states of water: Three physical forms of water are (a) liquid, (b) solid (ice) and (c) gas (water vapour). # The Author(s), under exclusive license to Springer Nature Singapore Pte Ltd. 2021 S. K. Saha, N. N. Pathak, Fundamentals of Animal Nutrition, https://doi.org/10.1007/978-981-15-9125-9_5

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5 Water

2. Water as a solvent: Water is a polar molecule means the centres of positive and negative charges are permanently separated by a short distance. This property is due to the structure of water molecule. The hydrogen (H) and oxygen (O) atoms are not present in straight line. Water is a good solvent for ionic solids and polar molecules readily dissolve in it. For example, sodium and chloride ions are closely bound in the common salt (Sodium chloride) due to positive (+) charge of sodium ion (Na+) and negative (
) charge of chloride ion (cl
). In the presence of water the attraction between sodium and chloride is weaken. 3. Hydrogen ion concentration (pH) of water (H2O) is neutral (7) and that of wholesome drinking water ranges between 6.8 and 7.2. 4. Thermal property of water: The amount of heat required to raise the temperature of 1 g water to 1oC is known as thermal capacity. It is very high for the water in comparison to other liquids, due to high heat holding capacity of the water. 5. Water takes more time for heating as well as cooling. 6. Boiling point of water: large amount of heat is required for the boiling of water which is 100  C (212  F) for H2O at normal pressure. 7. Freezing point: Cooling of water to the level of ice formation requires removal of large amount of heat from the water to bring down its temperature 0  C (32  F). 8. Specific density of water: At normal temperature and pressure weight of 1 ml (1 cc) water is 1 g. It means specific density of water is 1. However, it is a little higher at 4  C. This is due to compactness of water molecules. This is a characteristic feature of water different than the other liquids. Cooling below 4  C increases the volume of water due to which density of ice is less than the density of water. This property of water is very useful for the survival of aquatic lives of cold region like tundra.

5.3

Water Properties of Biological Importance

Properties of water have significant effect on the life of animals and the properties of water having significant effect on the body are specific heat, latent heat of evaporation, easy transportation of water in the body, solvent property, dielectric constant, catalytic action and lubricating action. 1. Specific heat or thermal property: Water requires large amount of heat for raising temperature of 1 g water to 1  C at normal pressure. This high heat holding capacity of water maintains the body temperature of animal in normal range. Liberation of heat in the body is a continuous process of biochemical reactions in the cells. 2. Latent heat of evaporation: Water has highest amount of latent heat of evaporation. Thus evaporation of water produces maximum cooling effect on the body.

5.4 Functions of Water in Animal Body

3. 4.

5.

6.

7.

31

Water vapour holding capacity of air is very high due to which air movement produces cooling effect by evaporating sweat. Body heat regulation by sweating and sweat evaporation. High solvent power of water is a remarkable property of biological importance. Water possesses high power of dissolving large variety of substances. Water forms two kinds of solution with different kinds of substances (solution), i.e., the true solution and the colloidal solution. Many substances are dissolved direct in the water while some other substances are dissolved by different kinds of aqueous solutions. For example, fats and fatty acids are not soluble in water but soluble in the bile solution of water. Dielectric constant: The dielectric constant of pure water (H2O) is higher than any other liquid except the hydrocyanide. It means oppositely charged particles can co-exist in water. It is a good inonising medium as it provides greater scope of chemical reactions. Catalytic action: Water has remarkable catalytic action due to ionizing ability, readiness to form intermediate compounds or some other physic chemical property. Water accelerates large number of chemical and biochemical reactions. All reactions in the living cells take place in the water medium. Dehydration reduces the rate of chemical reactions in the body cells and no reactions in the body cells and no reaction can take place in the absence of water. Lubricating action: Animal body contains many joints and rubbing surfaces which need protection from decaying effect of frictions. Water along with other dissolved and miscible substances forms effective lubricant, e.g. synovial fluid in joints, mucous secretion from epithelial cells saliva during eating and many others.

5.4

Functions of Water in Animal Body

One cannot imagine life without water. Major involvement of water in animals is the maintenance of normal metabolism, body temperature and physical structure. These are accomplished by the following functions. 1. Water is essential for metabolism: Water is essential for the various biochemical reactions in the cells necessary for the supply of energy and other nutrients required for various physiological functions. Fall in body water below the threshold level results in the occurrence of metabolic disorders. High level of water deficiency result is death. 2. Water as an essential substrate: The biochemical reactions involving hydrolysis require water as a substrate, e.g. hydrolysis of sucrose (C12H22O11) uses one molecule of water (H2O) for the production of two molecules of hexoses (2C6H12O6, i.e., one molecule each of glucose and fructose). 3. Water is a product of oxidation: Oxidation of glucose or any other hexose sugar for the supply of biological energy results in the production of carbon dioxide and water.

32

5 Water

C6 H12 O6 þ 6O2 ¼ 6CO2 þ 6H2 O þ Energy 4. Solvent action of water: Different kinds of biochemical constituents are readily dissolved in the water. The cytoplasm is mixture of colloids, crystalloids and ionized compounds. These states are essential for the normal biochemical reactions. Deficit of water results in the development of metabolic disturbances in the body. 5. Water is a transport medium in the body: Transportation of nutrients and metabolites in the body is carried by blood and lymph which joins different fluid compartments of the body contain more than 80% water in dynamic state. 6. Diluent function of water: Water is required in gastrointestinal tract for the digestion of foods and dilution of nutrients for facilitating absorption of nutrients into the body and different cells for metabolism. 7. Excretory function of water: Excretory metabolites dissolved, mixed and adsorbed in water are eliminated at regular interval from the body. The various excretory channels are faeces from the G.I. tract, urine through renal system, sweat through skin and volatile products in expired air.

5.5

Mechanism of Body Temperature Regulation by Body Water

The characteristics of water like high specific heat, high latent heat of evaporation and high thermal conductivity are responsible for the regulation of body temperature. These factors permit accumulation of heat within the limits of specific heat, then transfer of heat and finally loss of heat due to vaporization of water from the body surface and vapour in expired air. Exposer to heat increases body temperature which stimulates panting and sweating for the expulsion of body heat by evaporation of water in expired air and sweat on the skin. Highest heat loss occurs from the vaporization of sweat followed by respiratory vaporization.

5.6

Water Absorption

Water is absorbed from the different parts of the alimentary canal and significantly differs among the species. In the ruminants and pseudoruminants large volume of water is absorbed from the rumen, reticulum and omasum. Practically there is no absorption of water from the abomasums and stomach of non-ruminants and duodenum and small intestine of all species. The flow of fluid includes gastric juice, pancreatic juice, bile and intestinal secretion (succus entericus). The net inflow is quite high from the organs. Higher absorption of water carrying different nutrients occurs through the ileum, jejunum, caecum and large intestine. The amount of water

5.9 Factors Affecting Water Content of Body

33

left in faeces for excretion depends on the composition of diet and amount of water intake. Difference among the species is very high. The dung of cattle and buffaloes contain 75–83% water, while the faecal pellets of sheep, goats, camel, deer and antelopes contain 60–65% water.

5.7

Metabolic Water

The amount of water produced in the body of animals due to metabolism (oxidation) of organic components of foods (carbohydrates, proteins and fat) is known as metabolic water. Average values of metabolic water per gram of starch, fat and protein metabolism in the body are 0.6, 1.1 and 0.44 ml, respectively.

5.8

Body (Tissues) Water

Water is the largest component of body tissues constituting about 60% to more than 80% in different tissues except the depot fat. Water content in the body is affected by several factors like age, body condition, environment and food habits, etc. Water content in the body of lean animal is much higher than the fat (obese) animal of same age, sex and variety. The percentage of body water on the basis of fat free body tissues is almost similar for common animal species like bovine, ovine, caprine, swine and many varieties of fishes. Body water content ranges between 70 and 75% (average 73%) of fat free body tissues

5.9

Factors Affecting Water Content of Body

1. Effect of age on water content: Highest water content is present in foetus which decreases at a fast rate during the first week of life (Table 5.1). 2. Water content of different body tissues: Water content of dentum, adipose tissue and skeletal tissues is quite less. It is higher in cytoplasm and highest in cerebrospinal fluid (Table 5.2). Table 5.1 Effect of age on body water content

Age or stage Zygote Foetus At birth 8 days old Full grown (fat free body)

Water percent 90 (90) 86–88 (87) 81–85 (88) 75–80 (77) 70–75 (73)

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5 Water

Table 5.2 Water content in different body tissues

Body tissue Dentine Skeleton Adipose tissue Soft tissues except fat Cerebrospinal fluid Blood Saliva Semen

Water percent 9–12 (10) 14–50 6–20 68–86 99 90 99.5

Table 5.3 Effect of species and fodder on water content

Species Mammals Jelly fish Tadpole Berseem Doob

Water percent 60–80 93–96 88–92 85–90 75–85

3. Effect of species on body water content: large variation occurs in the body water content of different species (Table 5.3). Also the water content differs from different fodder and grasses.

5.10

Distribution of Body Water

All cells of a living organism contain water but percentage varies among the tissues.

5.10.1 Body Water Compartments Body fluids are initially differentiated into (1) intracellular fluid (ICF) present within the cell and that present outside cells is called (2) extracellular fluid (ECF). The ECF is further divided by the walls of the vascular system into the (a) interstitial fluid and (b) the plasma. Approximate distribution of body water has been worked out to be about half of the body weight within the cell content. Interstitial space contains about 15% and 5% in blood plasma. The other special ECF compartments are aqueous humour of ocular system, cerebrospinal fluid, pancreatic juice, bile, urine and cysternal milk in the lactating mammalian females. These special ECF are known as transcellular fluids.

5.13

Water Turn Over

35

5.10.2 Water Movement Amongst Body Fluid Compartments Water in different body fluid compartments is found mostly in dynamic state. Water molecules are easily cross cell membrane. However, in case of presence of osmotic or hydrostatic pressure gradient between the any body fluid compartments, a shift of water will take place. In absence of hydrostatic gradient, the water movement among different fluid compartments takes place for the maintenance of osmo concentrations of the fluids.

5.10.3 Methods of Measuring Body Fluid Volume In direct method whole body evacuated of excreta is dried at 100  2  C for the complete evaporation of water. The loss in weight due to drying or dehydration of the body water content which can be expressed as percentage of empty body weight. Indirect methods are based on the uniform distribution of a marker substance throughout the body fluid compartment within a short time.

5.11

Properties of Marker

1. It should be non-active and should not bind within the body. 2. Its distribution should be fast and uniform. 3. Normally, it should not be hazardous for the animals and public health.

5.12 1. 2. 3. 4. 5.

Some Common Markers Used

Urea dilution technique. Antipyrine dilution technique. Deuterium dilution technique (non-radioactive). Tritium dilution technique (radioactive) Dye dilution technique.

5.13

Water Turn Over

The rate of excretion and replenishing the tissue water maintaining the homeostasis is known as water turnover. It is variable in different subjects and influenced by species, age, sex, physiological state of the body and environment.

36

5.14

5 Water

Water Balance or Water Intake and Out Put

Compartmental body water remains almost constant. The metabolic losses of body water are periodically replenished by drinking water, metabolic water and water in foods/feeds. An example of water balance is shown in Table 5.4.

5.15

Thirst and Water Intake

The loss of water from the body is a continuous process. Eating, water drinking and excretion are the normal routine functions of the body. However, when water intake is delayed and excretion exceeds the normal water content of the body, a water deficit condition is created. This produces a sense of thirst resulting in change in behaviour for the search of water for drinking.

5.16

Sources of Compartmental Water

Body tissues receive water from drinking water, water in food or feed and metabolic water.

5.17

Sources of Drinking Water

Common sources of drinking water of animals are the rivers, lakes, ponds, wells and tube wells. Like human being most of the animal species do not drink brackish (Saline) water. However, some breeds and species of animals of coastal areas occasionally drink sea water, viz. Chilika buffalo of Odissa in India. Thirsty yaks eat ice. Table 5.4 Water balance or water intake and output

Fate of water I. Water intake Drinking water Food/Feed water Metabolic water Total water intake II. Water loss Faeces Urine Sweat Expired air Total water loss

Human (ml)

Cattle (l)

1500 1000 500 3000

23 5 2 30

100 1500 800 600 3000

12 8 2 8 30

5.19

5.18

Average Drinking Water Requirement of Different Classes of Farm Animals

37

Factors Affecting Water Requirement and Water Intake

The various factors affecting water requirement of body and water intake are physiological state of body, quality of feed and environment. 1. Physiological state of the body: The water requirement of an ideal animal is less due to less loss of body water. Water requirement increases in working animals due to more loss of water in expired air caused by increased respiration rate. Lactating females drink more water for milk secretion (water content in milk of different species ranges from 80 to 88%). Water requirement also increases significantly with the progress of pregnancy. More water is consumed by laying hens in comparison to nonlaying hens and cocks. 2. Sources and quality of feeds: In herbivorous animals drinking water requirement increases with the maturity of pastures and feeding of higher proportion of dry feeds. High fat content in the diet reduces drinking water requirement. 3. Environmental factors: Dry air, solar exposure and air movement increase body water loss by evaporation in expired air and body surface. This results in more water intake.

5.19

Average Drinking Water Requirement of Different Classes of Farm Animals

It is not justified to generalize the water requirement of farm animals and poultry. However, a guide line based on certain observations may be useful for the estimation of water requirement (Table 5.5). Table 5.5 Drinking water requirement of animals (approximate)

Animal species Growing cattle Adult cattle (idle) Bullock (working) Dry non pregnant cow Lactating cow Goat Sheep Swine, growing Finishing Pregnant Lactating Equine Camels Poultry, growing Layers Dogs

Drinking water 10–12% of body weight 8–10% of body weight 12–15% of body weight 8–10% of body weight 15–18% of body weight 8–10% of body weight 7–9% of body weight 10–12% of body weight 8–10% of body weight 8–10% of body weight 12–15% of body weight 8–12% of body weight 7–10% of body weight 10–12% of body weight 12–15% of body weight 8–10% of body weight

38

5.20

5 Water

Uses of Water in Nutrition and Feeding

1. Water is used for drinking. 2. Soaking of concentrate mixture for reducing dustiness and preventing sorting of selected ingredients from feed mixture. 3. Softening of dry and coarse fibrous roughages like straws and kadbi. 4. Soaking and washing of feeds containing antinutritional factors like oxalates and potassium salts in the paddy straw, mowrin (saponin) in the mahua seed cake and bitter principles in neem seed kernel cake, etc. 5. Reconstitution of good grains. 6. Cooking of concentrate mixture. 7. Preparation of gruel, slurry and soup, etc. 8. Sani making, i.e. preparation of fresh wet mixture of chaffed dry fodder, concentrate mixture and chaffed green fodder (if available) alongwith salt and mineral mixture. This is a palatable and tasty preparation for better digestibility. It is apopular among the farmers of mainly northern India. 9. Steam making for conditioning of pellets.

5.21

Quality of Common Drinking Water

Drinking water is normally obtained from the natural sources which generally contains certain dissolved and suspended substances. Pure water (H2O) is not considered suitable for drinking. In case of high concentration of suspended solids filtration and other treatments are required to make the water fit for drinking. No standard has been worked out for the drinking water of livestock and poultry. Running water of rivers and streams, lakes, ponds and canal is used for drinking. Purification of natural water sources is carried by the different varieties of aquatic plants. These plants utilize different kinds of dissolved and suspended substances. Some species of aquatic plants like water hyacinth, pistia, hydrilla, azolla and lemna also absorb heavy metals and alkaline compounds.

5.22

Need of Maintaining Water Quality

Due to excessive extraction of ground water excess of harmful substances like arsenic and chlorine is increased to harmful level. Likewise deficiency of useful elements like salts of iodine, zinc and copper are the causes of deficiency disease.

6

Carbohydrates

The organic compounds made up of carbon and water as the major constituents are known as carbohydrates. Often other substances are also found in many carbohydrates and these are called derived carbohydrates. The genesis of terminology “carbohydrate” from a French terminology “hydrate de Carbone” and it is used for all kinds of natural products containing carbon, hydrogen and oxygen. The hydrogen and oxygen in the ratio of 2:1 as in a water molecule. A general empirical formula for most of the carbohydrates is CnH2On or (CH2O) n. The ‘n’ is the number of particular element and it(n) is 3 or more. This formula is used for monosaccharides. Polymerization of hexoses for the production of disaccharides, trisaccharide and tetrasaccharides results in elimination of 1, 2 and 3 molecules of water, respectively. A further modification in general formula is required for denoting polysaccharides and derived carbohydrates. In some of the such carbohydrates, hydrogen and oxygen are not found in 2:1 ratio. The chemical composition and properties of such carbohydrates may differ due to the presence of non-carbohydrate moiety in the molecules. These may be aldehyde, ketone, acid, alkali, alcohols or their derivatives. The precise definition of carbohydrates may be the polyhydroxy compounds having either an aldehyde (–CHO) or a ketone (¼CO) group as in case of different monosaccharides. The polymerized compounds of monosaccharides are oligosaccharide and polysaccharides. The reduction products of saccharides are polyhydric alcohols. Oxidation products of saccharides are sugar acids (aldonic acid, aldaric acid and uronic acid). Replacement compounds yield various kinds of amino sugars (D-glucosamine and D-galactosamine).

# The Author(s), under exclusive license to Springer Nature Singapore Pte Ltd. 2021 S. K. Saha, N. N. Pathak, Fundamentals of Animal Nutrition, https://doi.org/10.1007/978-981-15-9125-9_6

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6.1

6 Carbohydrates

Production of Natural Carbohydrates

Vegetations are the store houses of carbohydrates synthesized by autotrophic nutrition from carbon dioxide and water. The energy for the synthesis is supplied by Sun (solar energy) and reactions occur in chlorophyll in the presence of light as shown in Fig. 6.1.

6.2

Distribution of Carbohydrates

Carbohydrates are the largest organic compounds on the earth. These constitute 50–90% of the dry matter of different plant species. Polysaccharides particularly the cellulosic compounds are more abundant among all kinds of carbohydrates present in the plants. However, variation among the plant species is very high and organ as well as tissue specific carbohydrates are also found. For example, simple sugars are generally found in fruits of grapes, mango, lichi, banana and many others. The sap of sugarcane plant is rich in sugar. Tubes, roots food grains and seed kernels are rich sources of starch. Grasses and trees are rich in fibrous polysaccharides like cellulose and hemicelluloses. The carbohydrates found in small amount in animal body are glucose in blood circulation and glycogen (animal starch) in other tissues. These are obtained from the plant sources in foods/feeds.

6.3

Significance of Carbohydrates in the Diets

Humans and animals need energy for the proper function of the body for maintenance of life. It is well known that greater part of diets of animals, bird and humans is made up of different kinds of carbohydrates. Starch constituents bulk of the diets of simple stomached animals (including primates) and birds. The fibrous cellulosic carbohydrates in herbages constitute bulk of the diets of ruminants and herbivorous non-ruminant animals and ratites. Carbohydrates are not essential for the supply of blood glucose essential for the vital functions in the body. Blood glucose can be supplied from the metabolism of fats and proteins through the process of gluconeogenesis, the process which prevails in the carnivorous animals like felines and canine. For herbivorous and omnivorous animals vegetable foods are practically essential and maintenance of life on carbohydrate free diets of fats and proteins for energy supply is only for short duration experimental demonstration. Moreover, for proper satiety, digestive activities and

6CO2+6H2O + 673 Kcal Solar Energy

Fig. 6.1 Glucose production in photosynthesis

Cholorophyll +Light C6H12O6+H2O

6.4 Importance of Carbohydrates for Physiological (Vital) Functions

41

maintenance of psychological health feeding of natural sources of carbohydrates are necessary. In the present global situation and agricultural crop production, the carbohydrates are still the cheapest source of dietary energy for the animals and birds.

6.4

Importance of Carbohydrates for Physiological (Vital) Functions

Carbohydrates are easily available natural gift of chemical form of energy essential for carrying optimum physiological functions. Adequate supply of metabolizable carbohydrates spares proteins (amino acids) for growth and repair of body tissues. The importance of dietary carbohydrates may be listed as follows: 1. Supply of biological energy: The carbohydrate circulating in blood in glucose and its polymer glycogen (animal starch) is stored in liver and nucleus. The amount of glycogen is very small. Metabolism of one molecule of glucose by oxidative phosphorylation yields 38ATP for supplying biological energy for vital functions. 2. Protein sparing action: In deficient supply of energy yielding nutrients like carbohydrates and fats, the proteins (amino acids) are metabolized for the supply of blood glucose by the process of gluconeogenesis. On adequate dietary supply of carbohydrates there is no need of utilization of proteins for the supply of energy (glucose) in the body. This effect is known as protein sparing action of carbohydrates. 3. Oxidation of proteins and fats: For the initiation of oxidation of proteins and fats a small amount of glucose is essential for starting the reactions of the tricarboxylic acid (TCA) cycle or Kreb’s cycle or citric acid cycle. In the absence of adequate supply of glucose, the metabolism rate of fats and proteins is increased for the production of glucose, essential for energy supply. This process of oxidation generally remains incomplete causing accumulation of ketone bodies (acetoacetic acid, β-hydroxybutyric acid and acetone). High accumulation of ketone bodies beyond threshold results in the occurrence of ketosis, a clinical condition. 4. Carbohydrates of animal body tissues: Very small amount of sugars and glycogen is found in the animal body tissues. The sugars are involved in regulation of metabolism in the body, viz., a. Deoxyribonucleic acid (DNA) and ribonucleic acid (RNA) are responsible for the transfer of genetic information of the cells. The sugars, deoxyribose and ribose are the constituents of DNA and RNA, respectively. b. Glucuronic acid is produced from the oxidation of UDP-glucose, glucuronic acid is found in liver and it is also a component of several mucopolysaccharides. Glucuronic acid in liver is a detoxifying agent and helps in the removal of different toxic chemicals and microorganisms through amalgamation and excretion.

42

6 Carbohydrates

c. Hyaluronic acid: It is a disaccharide composed of glucuronic acid and glucosamine. It is a viscous material and forms the matrix of connective tissues. d. Heparin: It is nucleopolysaccharide made up of chains of glucuronic acid and sulphate group containing glucosamine. Its molecular weight is high (about 2000 kDa) and processes very effective anticoagulant property. H

COOH

H

O

CH2OH

O

O

OH

H H OH -O

H

H OH

H OH

H

NHCO.CH32

H

( - glucoronic acid) + (N = acetylglucosamine) Hyaluronic acid

e. Chondroitin sulphates: These are constituents of different kinds of connective tissues like cartilages, bones, tendons and skin. It has a polysaccharide sulphate in a chain structure of glucuronic acid with N-acetyl galactosamine sulphate. f. Glycosides: These are complex compounds synthesized by condensation of a monosaccharide molecule with the hydroxyl group of another compound which may or may not be a monosaccharide. Different kinds of glycosides are found in various species of plants. Most of the glycosides produce toxic substances on hydrolysis in the digestive system. Some of glycosides have also therapeutic values.

6.5

Classification of Carbohydrates

There is great variation in different kinds of carbohydrates. Main constituents of carbohydrates are carbon and water but some kinds of carbohydrates also contain nitrogenous compounds, lipids, etc. The properties of carbohydrates are significantly affected by the number and position of carbon, hydrogen and oxygen in the structure besides the presence of non-carbohydrate constituents. Due to these diversified conditions the classification of carbohydrates is some what complex. However, considering main qualitative and quantitative characteristics of different carbohydrates and also non-carbohydrate features, the carbohydrates may be classified into (1) sugars, (2) non-sugars and (3) carbohydrate like substances Fig. 6.2). Monosaccharides are the simple sugars of first order and include molecules containing 3–7 of CH2O, on the basis of which these simple sugars are named as trioses (C3H6O3), tetroses (C4H8O4), pentoses (C5H10O5), hexoses (C6H12O6) and heptoses (C7H14O7). So far, there is no evidence of existence of trioses and tetroses

6.5 Classification of Carbohydrates

Fig. 6.2 Classification of carbohydrates on the basis of sugars and non-sugars

43

44

6 Carbohydrates

Fig. 6.2 (continued)

in natural products and these are intermediary stages in the metabolism of higher carbohydrates. The other groups of higher sugar molecules are the oligosaccharides (oligo means two). These are di-, tri- and tetra saccharides formed by bonding of two, three and four molecules of monosaccharides with elimination of one water molecule at each linkage as follows (Fig. 6.3):

6.8 Structures of Some Important Monosaccharides Fig. 6.3 Sucrose formation from glucose and fructose

C6H12O6 Glucose

+

45

C6H12O6

C12H22O11 + H2O

Fructose

Sucrose

water

The polymers of less than 10 molecules of monosaccharides are included in the oligosaccharides. The polymers may be made up of identical or different monosaccharides in large number forming straight or branched chain molecules. The polysaccharides are non-sugar carbohydrates because these are not sweet in taste. The polysaccharides are further divided into (1) homoglycans formed of only one kind of monosaccharide units, and (2) heteroglycans formed by the polymerization of different kinds of monosaccharides, and number and nature of the other derivatives. The molecular weight of polysaccharides ranges from 8000 in fructans to hundred million in amylopectins. A separate group of polysaccharides contain highly diversified compounds due to the presence of non-carbohydrate constituents in their molecule. The carbohydrates found in free form starts from pentoses. Hexoses and disaccharides (sucrose) are most common in human diets as sweeteners.

6.6

Classification of Carbohydrates on the Basis of End Products

The carbohydrates found in vegetation and animals can be classified on the basis of end products on hydrolysis. Such carbohydrates along with their sources are presented in Table 6.1.

6.7

Monosaccharides or Simple Sugars

Monosaccharides cannot be hydrolyzed further for the production of smaller sugar molecules. The monosaccharides of less than six carbon atoms are rarely found in free form in the natural products. The monosaccharides are further classified into (1) aldoses and (2) ketoses. The former contain an aldehyde group (–CHO) and the latter contains a keto group (¼CO) in their molecular structures as shown in Table 6.2.

6.8

Structures of Some Important Monosaccharides

1. Structure of trioses: These are compounds of three carbon atoms and three molecules of water. One of the carbon linkages in the sugar molecule is either aldehyde (glyceraldehydes) or a ketone (Dihydroxyacetone) as shown in Fig. 6.4. 2. Structure of Tetroses: These are made up of four carbon atoms arranged in a chain or ring structure (Fig. 6.5)

46

6 Carbohydrates

Table 6.1 Classification of carbohydrates on the basis of hydrolytic products and their sources Carbohydrates hydrolysis products Common sources including foods/feeds I. Monosaccharides A. Pentoses (C5H10O5) 1. Arabinose Gum of plants like gum Arabic from Acacia spp., some sea foods and acids of meat products 2. Ribose Living cells of plants and animals as constituent of RNA, DNA, ADP, ATP and some enzymes 3. Xylose Pentosans present in plants, leaves, flowers, fruits and wood B. Hexoses (C6H12O6) 1. Glucose Ripen fruits, honey, flowers, tender leaves, fruits, roots and tuber (Aldose) 2. Fructose Fruits, tender leaves, flowers, honey and some tubers (Ketose) 3. Galactose Milk sugar and galactosides of brain and nervous tissue 4. Mannose Mannans in plants, globulins and some egg proteins II. Nutritional importance of disaccharides and trisaccharides is more than the Oligosaccharides other oligosaccharides A. Disaccharides ((C12H22O11) 1. Sucrose Glucose + Fructose Sugarcane, sugar beet and other plants 2. Lactose Glucose + Galactose Milk of all mammals 3. Maltose 2 moles of glucose Barley sprout, malt products III. Polysaccharides A. Homo-polysaccharides A1. Glucans (yield glucose on acid hydrolysis) 1. Starch Glucose Grains, seeds, fruits, tubers, roots etc. 2. Dextrin Glucose Intermediate products of starch degradation 3. Glycogen Glucose Liver, muscles (animal starch) 4. Cellulose Glucose Most part of structural constituents of plants. A2. Fructans (acid hydrolysis product is fructose) 1. Insulin Fructose Some plant species 2. Levan Fructose Some plant species B. Heteropolysaccharides (acid hydrolysis products are different monosaccharides) 1. Hemicelluloses Arabinose, xylose, Different parts of plants including seed coat glucose, mannose, uronic (Testa) acid 2. Pectins Galacturonic acid + Middle lamella of most of the plants rhaminose 3. Gum Monosaccharides + uronic Exudates, bark and leaves of many plants acid 4. Mucilage Monosaccharides + Aloe, gingilly leaves, hibiscus (Chinese disaccharides + uronic acid shoe) flower and many plants, linseed

6.8 Structures of Some Important Monosaccharides

47

Table 6.2 Aldose and ketose monosaccharides Monosaccharides Trioses Tetroses Pentoses Hexoses Heptoses

Aldoses Glyceraldehyde Erythrose Arabinose, ribose, xylose Glucose –

Ketoses Dihydroxyacetone Erythrulose Ribulose and xylulose Fructose D-sedoheptulose

Fig. 6.4 Structure of Trioses, i.e. Glyceraldehyde and Dihyroxyacetone

Fig. 6.5 Structure of tetrose

3. Structure of pentoses: The pentose sugars as depicted by a common formula C5H10O5. Some of the important pentose sugars are (1) aldehyde group (–CHO) containing pentoses like α-L-arabinose, α-D-xylose and α-D-ribose, and (2) ketone group (¼CO) containing keto-pentoses like D-xylulose and D-ribulose (Fig. 6.6) a. L-Arabinose: It is an aldopentose found in the form of pentosans in Arabinans. L-arabinose is a constituent of hemicelluloses and may be detected in silage due to hydrolysis of Arabinose. Gum of acacia plants like gum Arabic also contains L-arabinose. b. D-xylose: It is a constituent of pentosans present in Xylans in association with Arabinose. These are generally found in hemicelluloses of grasses which yields Xylose on hydrolysis with sulphuric acid. c. Ribose: It is an essential constituent of ribonucleic acid (RNA) present in all living cells and also in some of the vitamins and enzymes.

48

6 Carbohydrates

Fig. 6.6 Structure of Pentoses (a) and Hexoses (b)

6.9

Hexoses

The hexoses are represented by a common formula C6H12O6 and found as aldoses and ketoses. Some of the hexoses like glucose and fructose are present in fruits and green herbages as free as well as in combined form. Four hexoses of nutritional significance are glucose, fructose, mannose and galactose. 1. D-Glucose: It is commonly known as grape sugar, for which the preferred therapeutic term is dextrose. Glucose is present in free form in fruits, green plants, honey and blood, lymph and cerebrospinal fluid of the species of animal kingdom. 2. D-Fructose: It is also known as fruit sugar levulose. It may occur in free as well as in polymerized from. Free fructose is found in sap of green plants, fruits and honey. In pure form both glucose and fructose are white and solid crystals. The fructose is more sweeter than the glucose and common sugar (sucrose). 3. D-Mannose: It is always present in polymerized form as mannon and constituent of glycoproteins. The mannons are widely distributed in bacteria, yeasts and moulds. 4. D-Galactose: It is a constituent of milk sugar lactose and does not occur free except during the fermentation of milk. In addition to milk galactose has also been found as the components of galactolipids, mucilages, natural gums and anthocyanin pigments (Fig. 6.6b).

6.9 Hexoses

49

Keto-pentoses, D-xylulose and D-ribulose are found as intermediary products in the form of phosphates in the pentose-phosphate metabolic pathway as follows (Fig. 6.7) Isomeric forms of hexoses are quite common and these may be 16 stereoisomers equally divided into D (dextro) sugars and their mirror image L (levo) form. On the other hand ketoses may occur in 4 D-forms and 4 L-forms. Both open chain and ring structure of sugars may be present. Pyran and furan are the six and five carbon ring structures, respectively, and these monosaccharides are also known as pyranose and furanose. The ring structures are shown as follows (Fig. 6.8): The open chain structures of two forms of glucose shown as follows: Ketogluconate-6-phosphate CO2 Ribulose-5-phosphate

Xylulose-5-phosphate

Ribulose-phosphate-3-epimerase RibosePhosphate Isomerase

Ribose-5-phosphate

Fig. 6.7 Pentose Phosphate Metabolic Pathway

Fig. 6.8 alpha-pyrene and furan

50

6 Carbohydrates

In fresh water solution pure α or pure β form of D-glucose is converted into other form through open chain form to attain equilibrium. This process is called mutarotation. The α-D-glucose is not a true isomer of β-D-glucose due to this difference they are called anomers.

Many derivatives of α and β forms of D-glucose are found in nature. Polymerization products of αβ form of D-glucose are starch in plants and glycogen (animal starch) in animals. Polymer of β form of D-glucose is cellulose.

6.10

Derivatives of Monosaccharides

Different derivatives of monosaccharides are the (1) phosphoric acid ester, (2) amino sugars, (3) deoxy sugars, (4) sugar acids, (5) sugar alcohols and (6) glycerides.

6.10

Derivatives of Monosaccharides

51

1. Phosphoric acid esters: These are produced from esterification either at carbon atom 1, 6 or both of D-glucose. These phosphates i.e. α-D-glucose 1-phosphate or α-D-glucose-6 phosphate are actively involved in several metabolic reactions in the living bodies as evident from the following reactions of glycolytic pathway of glucose metabolism. In presence of hexokinase ATP and Mg ADP D-glucose H 2O

Glucosephophate Isomerase

H2 O

Phosphate in presence of glucose-6-phosphatase

Fructose 1,6-di phosphate

6 - Phosphofructokinase ADP and Mg ATP H2O

Phosphate

Fructose-6phosphate

Hexosephosphatase

The structural formulae of a-D-glucose L-phosphate and α-D-glucose-6- phosphate are shown as follows:

D-glucose-1-phosphate

D-glucose-6-phosphate

Amino sugars: The amino sugars are produced from the replacement of carbon atom at position 2 of an aldohexose by an amino group (–NH2). Two nutritionally important amino sugars are (1) β-D-glucosamine present in chitin and (2) β-Dgalactosamine present in cartilage. 2. Deoxy sugars: These sugars are produced by the replacement of a hydroxyl (OH) group by hydrogen. The derivative of ribose is deoxyribose, which is a constituent of deoxyribonucleic acid (DNA). The deoxy derivatives of galactose and mannose are fucose and rhamnose, which are presented in some heteropolysaccharides. 3. Sugar acids: Sugar acids are the oxidation products of aldoses. A few important sugar acids are aldaric, aldonic and uronic acids. The general formulae of these three types of sugar acids are shown as follows:

52

6 Carbohydrates

Among various sugar acids, the uronic acids produced from glucose are glucaric, gluconic and glucuronic acids, and those derived from galactose are the galactaric, gluconic and galacturonic acids. The acid sugars are the constituents of many heteropolysaccharides. 4. Sugar Alcohols: The reduction products of simple sugars are the polyhydric alcohols like sorbitol from glucose and dulcitol from galactose. Mannitol is a reduction products from fructose as well as mannose. Reduction of fructose in green grasses by anaerobic bacteria during the process of fermentation for silage making yields mannitol.

5. Glycosides: There are produced by the replacement of the hydrogen of the hydroxyl group at anomeric carbon atom of hexoses by esterification or nomenclature with an alcohol or a phenol. The specific nomenclature of the glycosides depends on the sugar used in the reaction, viz. glucose yields glucosides, fructose yields fructorides and galactose yields galactosides. The linkage at anomeric carbon atom of the sugar is known as glycosidic bond.

6.12

Disaccharides

53

The most abundant glycosides present in the nature are the oligosaccharides and the polysaccharides, which produce sugars and various derivatives of sugars on hydrolysis. The non-sugar constituent is also found in some of the natural glycosides, viz. adenosine is formed of a heterocyclic nitrogenous base the ademine and D-ribose with alimination of a water molecule as follows:

Some of the glycosides are cyanogenic, which produces hydrogen cyanide (HCN) on hydrolysis in the digestive system of the animals causing fatal effects. The plants containing cyanogenic glycosides are highly toxic for the animals. Actually glycosides are not toxic but their enzymatic hydrolysis produces HCN which is highly toxic. Some of the cynogenic substances are dhurrin in sorghum and Sudan grass forages, linamarin or phaseolunatin in linseed, tapioca and java beans, and amygdalin found in the seeds of apple, plums, Chemise, peaches and bitter almonds.

6.11

Oligosaccharides

These are higher sugars made of two or more molecules of hexoses. There are three types of disaccharides and a trisaccharide which are nutritionally important. The disaccharides are sucrose, lactose and maltose and the trisaccharide is raffinose.

6.12

Disaccharides

Disaccharides are the condensation products of monosaccharides and there are scope of formation of a large number of disaccharides through the combination of two same or different monosaccharides in different structures like maltose and cellobiose which are made of two molecules of β-D-glucose but differ in properties due to difference in their structures. The disaccharides of nutritional importance are cane sugar or sucrose, milk sugar or lactose, maltose and cellobiose. The latter two are not found in free form. Hydrolysis of disaccharides yields two hexoses as follows:

54

6 Carbohydrates

C12H22O11 +H2O

Acid or Enzymatic

2C6H12O6

Hydrolysis

Sucrose It is the cane sugar and also known as common sugar or table sugar. Sucrose is widely present in many plans, fruits, flowers and roots. Sugar cane and sugar beet are considered to be the most concentrated source of sucrose yielding 18–20 and 15–20% in fresh materials, respectively. Sucrose is a condensation product of one molecule each of β-D-glucose and β-Dfructose combined by an oxygen bond joining their anomeric carbon atoms in ring structure. Due to this type of configuration sucrose does not have a reducing group.

Lactose It is milk sugar present in the milk of all mammalian species. Lactose is less sweet and less soluble than the sucrose. It is a condensation product of one molecule each of β-D-glucose and β-D-galactose joined by β (1-4) bond forming an active reducing group making lactose a reducing sugar.

The content of lactose is variable in the milk different species ranging from 2 to 8% in fresh milk. Mean value of lactose in the milk of cow, buffaloes, goat, sheep, mare, donkey, dog, cat and women is 4.8, 3.5, 4.2, 4.7, 6.9, 6.2, 3.5, 4.4 and 7.3, respectively. Lactose content in milk of mare and donkey is much closer to that in women is milk. Lactose is highly fermentable due to which keeping quality of fresh milk on room temperature in tropical countries is very short. Milk is easily infected by lactic acid producing bacteria in any form which causes fermentation due to production of lactic acid from lactose resulting in caogulation of milk solids and souring of milk.

6.12

Disaccharides

55

Maltose It is made of two molecules of a-D-glucose joined by a reducing group at α-1,4 positions making it a reducing sugar. Maltose is a hydrolysis product of starch and glycogen as usual due to activation of enzymes or dilute acids. The most common example of maltose production is the production of malt by controlled germination of barley. The dried product of malt which is used for the production of popular fermented beverages like beer and malt whisky. Maltose is much less sweet than the sucrose and soluble in water.

Cellobiose It is not found in free form in the natural products. Cellobiose is made up of two β-D-glucose molecules joined by a β (1-4) linkage. There is no effect of digestive enzymes of the mammals on cellobiose which escape unchanged. However, cellobiose is split by the enzymes produced by the microorganisms inhabiting the specialized compartments of digestive tract of different animals, birds and other species, specially the herbivorous animals. Cellobiose contains one active reducing group and it is a reducing sugar.

Trisaccharides Two trisaccharides have been detected in the natural products. These are raffinose and kestose, the former is more common and may be found in plants along with sucrose. Molasses and cotton seeds contain appreciable amount of raffinose. Raffinose is made up of one molecule each of glucose, galactose and fructose.

56

6 Carbohydrates

The other trisaccharide, kestose and its isomeric form isokestose are present in the green parts and seeds of herbages. These are the products of a sucrose molecule linked with a fructose molecule. The common formula of trisaccharides in C18H32O16 and on hydrolysis yields three molecules of hexoses as follows: C18 H32 O16 þ 2H2 O ¼ 3C6 H12 O6 Tetrasaccharides Stachyose, a tetrasaccharide is present in most of the herbages and is as common as raffinose. The sugar has been detected in more than 150 species of plants. Stachyose is a non-reducing sugar and on hydrolysis yields one molecule each of glucose and fructose and two molecules of galactose. The tetrasaccharides are represented by C24H42O21 and on hydrolysis yields four molecules of hexoses (C6H12O6). Polysaccharides The non-sugar polymerization products of sugars of high molecule weights are known as polysaccharides (poly means many and saccharide means sugar). These are the largest amount of carbohydrates present in the nature and constitute the structural components of vegetations or reserve foods for use in scarcity and during germination of seeds etc. The polysaccharides are also denoted as glycans, which are (1) homoglycans and (2) heteroglycans. Lignin is quite close to polysaccharides and for very long period it has been described with polysaccharides for nutritional purposes. 1. Homoglycans: These are polymerization products of pentoses and hexoses but do not exhibit their reactions shown by aldose and ketose sugars. The common homoglycans are arabinans, xylans, glucans, fructans, galactans, mannans and glucosomanans. 2. Heteroglycans: These are mostly derivatives of polysaccharides and hydrolysis products may be acids and amino acids besides the sugar molecules.

6.13

Homoglycans

1. Arabinans: These are polymerization products of arabinose (a pentose) and mostly present in plants as a component of heteroglycans as in pectic materials, hemicelluloses, gum and mucilages, etc. 2. Xylans: these are high molecular weight polymers of xylose found in combination with may heteroglycans that of arabinans. 3. Glucans: Starch, glycogen, dextrin (an intermediate product of the hydrolysis of starch and glycogen), cellulose and callose are the common glucans present in plants except the glycogen present as an energy reserve in animal tissues.

6.13

Homoglycans

57

a. Starch: It is a reserve food present in all the plants. The seeds, tubes, roots and other parts of the plants. The starches are present in granular form of variable shape and size depending on the sources. Starches are primarily made up of glucans but small quantities of protein, lipids and phosphorus compounds are also found, which often significantly affect the properties of starches. Most of the starches are the polymers of two polysaccharides of different configuration. These are ammylose and ammlopectin. The later constitute more than 70% of the starch molecule. The detection of starches in foods/ feeds in quite easy as ammylose gives deep blue and amylopectin gives bluishviolet colour reaction with iodine solution. Amylose is mostly a linear chain which is made up from the linkage of α-Dglucose residues between carbon of previous molecule with carbon atom 4 of subsequent molecules with derivation in a small fraction of α-1-6 linkages. The structure of amylopectin is bush like due to presence of reasonably good number of α-1-6 linkages with main α-1-4 linkages. Physical properties of starch granules differ from each other in many aspects. These are insoluble in cold water and on heating swelling of granules occurs causing gelatinization. Swelling of starch granules of potatoes is much higher than the swelling of starch granules of cereal grains due to which the granules of potato explodes on soaking in hot water. Among the common foods starch content is quite high in rice, maize and wheat (65–75%) followed by cassava root, beet root, potatoes, barley and oats (50–65%) when compared on dry matter basis. Starch content in most of the foods is quite low and ranges from less than 1 to 20 percent on dry matter basis being low in cereal straws and high in lush green fodders and tuberous crops. Structures of starch and amylopectin are shown as follows:

The number of this unit in a molecule may be 100–1000.

58

6 Carbohydrates

Glycogen also known as animal starch is a highly branched chain polysaccharide synthesized from the polymerization of glucose molecules similar to amylose. Greater part of glucose molecules in glycogen are linked by α-1,4-glycosidic acid bonds along with some 10 present branched chain α-1,6-glycosidic acid bonds. Ingestion of glycogenic materials results in the synthesis of glycogen which is stored in granular form in the cytosol of different tissues in the body of animals. Maximum concentration of glycogen is found in the liver of animals which may be up to 8 percent of fresh weight. In other tissues glycogen concentration is normally contained below 1%. Muscle glycogen is produced from glucose in the muscle cells and partly also contributed by the liver which is the main site of glycogenesis. The molecular weight of glycogen molecules in highly variable, which is influenced by the species of animal, physiological state and the tissue of animals where synthesis occurs. Molecular weight of glycogen synthesized in liver is generally more than the molecule synthesized in the muscle cells. Glycogen is also present in the body mass of microorganisms. b. Dextrins: These are not present in free from and produced as an intermediary product during the hydrolytic disintegration of starch and glycogen during metabolism. The size of dextrin molecules is highly variable and may be differentiated into higher group producing red colour on reaction with iodine

6.13

Homoglycans

59

and smaller group producing no colour reaction with iodine. These water soluble carbohydrates are formed gum like viscous solution and impart characteristic pleasant flavour to products produced by the cereal grains, flour and flakes, etc. Amylase Starch

Amylase Dextrins

(H+)

Maltase Maltose

(H+)

Glucose (H+)

c. Cellulose: It is an largest proportion of carbohydrates presence in vegetation and main structural component of cell wall of herbages. Spindle shaped elongated cells of cotton fibre are almost pure cellulose. Good quality filter papers like Whatman brand are purest form of cellulose. Fibrous crop residues like straws and stovers contain 20–40% cellulose, whereas wood contains more than 50% cellulose.

The cellulose molecules are highly variable in size and normally made up of a chain of 2000–3000 β-D-glucose units linked by β-1-4-glycosidic bonds. The partial hydrolytic product of cellulose is a disaccharide, cellobiose and complete hydrolysis products are numbers of β-D-glucose. The repeating unit in the chain of cellulose is cellobiose. The cellulose chains is a result for the formation of the fibriles which then ultimately formed a compact fibrous structure for providing strength to the plants. d. Callose: Polysaccharides formed of β-1-3 glucose and β-1-4 glucose linked residues are collectively known as callose. Callose (β-glucans) is the component of higher plants for providing strength to cell walls during the particular stages of growth like grain formation and healing of wounds or infected parts of the plants. 4. Fructans: These are stored energy in roots, stems, leaves, flowers, fruits and seeds of many types of plants. The numbers of compositae and gramineae families are the rich sources of fructans. However, members of gramineae family only growing in temerate climate contain fructans. The molecular weight of fructans is mostly less than the glucans. Fructans are soluble in water and these are

60

6 Carbohydrates

polymers of β-D-fructose linked together by 2, 6 or 2, 1 bonds. These can be differentiated into three groups, viz. (1) levan group formed of 2, 6 linkages (2) insulin group composed by 2, 1 linkages and (3) a special compound of branched fructans made of both type of bonds, and present in the endosperm of wheat and in rye grass (Lolium perenne) and couch grass (Agropyron repens). Hydrolysis products are greater proportion of D-fructose with small fraction of D-glucose produced from the hydrolysis of the last segment of sucrose in a fructan molecule as evident from the following structural part (F. 6.22).

5. Galactans: These are also present in grasses of temperate region and may constitute about 6–9% of dry matter. These are polymerized large molecules of galactose mainly present in the stem of grasses. Galactans are also present in the seeds of leguminous crops like alfalfa, berseem and other cloves. utilized for the supply of energy for the germination of seeds. 6. Mannans: These are produced in the seeds of some palm species and made of mannose polymers. Endosperm of the seeds of tagua palm (Phytelephas macrocarpa) contain some amount of mannans. 7. Glucosomanans: Glucosomanans are the polymerization products of glucosamines. Chitin is a common glucosomanan made of linear linkage of acetyl-D-glucosamine is found in lower animals and lower plants. Crustaceans, fungi, moulds, some algae and other plants contain good amount of glucosomanans which provide structural strength.

6.14

6.14

Heteroglycans

61

Heteroglycans

These are polymerization products of different types of carbohydrate units, which are largely divided carbohydrates. Hemicelluloses, pectic products, gums, mucilages, chondroitin and hyaluronic acid are the common heteroglycans widely distributed in the natural products. 1. Hemicelluloses: These are widely distributed in cell wall of plants in association with cellulose. However, chemically it has little relationship with cellulose. Hemicelluloses are the polymerization products of variable units of D-glucose, D-galactose, D-mannose, D-xylose and D-arabinol in different kinds of glycosidic bonds. Some of the hemicelluloses may also contain uronic acid units. Xylan, the polymer of β-1-4-D xylose having side linkages of methyl-glucoronic acid is the main unit of hemicelluloses of grasses. There may also contain molecules of glucose, galactose and arabinose providing a complete structure to hemicelluloses. 2. Natural gums: These are exudates oozing from the cuts or other wounds on the plants. Gums are largely present in the barks and also in leaves. Natural gums are mostly the salts of calcium and magnesium often having hydroxyl esters like acetates. Gum of acacia plant is well known to people since time immemorial and widely used as binder and also in preparation of different food items. The molecules of gum arabic are made from the polymerization of arabinose, galactose, rhamnose and glucuronic acid units. 3. Mucilages: These are also known as acidic mucilages due to presence of galacturonic acid in their molecules. These are the constituents of seeds, leaves, roots, tubes and bark of different kinds of plants. Linseed is a high source of acidic mucilage which is commonly used in the foods of humans and animals. The hydrolysis products of linseed mucilage are the arabinose, galactose, rhamnose and galacturonic acid. The main difference in the molecules of gums and mucilages are the acid units. 4. Pectic substances: There are different kinds of closely related carbohydrate derivatives. These are structural components of cell walls and also the intercellular space of plants. Soft tissues of plants, fruits, tubers and roots are the main sources of pectic substances. These are soluble in hot water and abundantly present in the sugar beet and outer cousing of the oranges, lemon and other citrus fruit. Pectin the representative member these substances is made of the molecules of D- galacturonic acids linked in a straight chain and some units of methyl esters of galacturonic acid are also found in the chain. In addition to these molecules of L-arabinose, D-galactose and D-xylose also form side chains. The other important pectic substance is the pectic acid and is different from pectin is the absence of methyl ester of galacturonic and the molecule. There are rich sources of gel forming material suitable for the preparation of good quality jams of desirable consistency. 5. Hyaluronic acid: It is a polymer made of the units of D-glucuronic acid linked with an amino acid. The molecule of hyaluronic acid contains

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6 Carbohydrates

acetyl-D-glucosamine. Hyaluronic acid in the constituent of dermis of animals and synoil fluids, and also the unbiblical cord. This is a very important lubricant essential for the free movements of skeletal joins of the body. 6. Chondroitin: The derived sugar molecule is chondroitin is D-galactosamine, otherwise it is similar to that of hyaluronic acid. Sulphate esters of chondroitin make the structural parts of cartilage, tendons, ligaments and bones. Lignin Lignin is not a carbohydrate. Since nutritional contribution of lignin is negligible little attention has been paid for its exploration as a nutrient. Earlier, it was considered totally indigestible due to which for long time it was used as internal marker for the indirect estimation of herbage intake and digestibility by the grazing animals. In plant it provides strength to plants and resistance from the effects of chemical substances and biological to cells. Lignin is a group of closely related chemical compounds made from the polymerization of compounds from the three derivatives of phynyl-propane. These are crumaryl alcohol, coniferyl alcohol and sinapyl alcohol. The molecules of lignin are variable in structure and highly complex. Lignin due to its affinity for many polysaccharides and cell wall proteins interferes in their digestibility and reduces their availability for supplying nutrients to body. By this process lignin works as an antinutritional factor in the fodders of livestock as it forms complexes with hemicellulose and cellulose. Some units of lignin also contain nitrogen. The proportion of three aromatic alcohols in the molecule of lignins significantly influence their solubility in alkali solution which is highest for the lignin in (non-leguminous fodders) containing high proportion of p-coumaryl alcohol in the comparison to about 14% soft wool and only 4 percent in hardwood lignin containing about 15–16 and 21–22% methoxyl units respectively. The percentage of coniferyl alcohol is about 80 and 56% and that of sinapyl alcohol is 6 and 40% in lignin molecules of soft and hard wood, respectively.

Average content of fibrous components of some common feeds and other substances is shown in the following Table 6.3.

6.15

Fibre in Human Diets

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Table 6.3 Average values of cellulose, hemicellulose and lignin in some plant materials (percent on dry matter basis) Plants/substances Berseem Lucerne Wheat straw Paddy straw Maize stover Sorghum stover Pearl millet stover Groundnut shells Sugar cane bagasse

6.15

CP 17–23 19–24 3.5–4.0 3.0–4.0 4.0–9.0 5.50–20.50 7.5–8.9 4.0–5.0 2.1–3.0

Cellulose 20–24 20–25 30–45 30–45 49–59 13.0–45.0 25.0–35.0 32.0–37.0 33.0–40.0

Hemicellulose 7–12 7–8 20–25 20–25 35–40 13.85–30.0 25.0–30.0 15.0–25.0 20.0–25.0

Lignin silica 0.5–1.3 0.8–1.0 15–20 15–20 7.5–10 5.0–24.0 6.5–8.5 15.0–25.0 10.0–20.0

Fibre in Human Diets

The nutritional requirements of herbivorous animals are met from the adequate intake of a mixture of herbages because they are capable of extracting nutrients through the active participation of symbiotic microorganisms in the modified and enlarged compartments of the alimentary canal. These animals particularly are ruminants, pseudorminants and those are with larged caecum and colon which are capable of digesting structural carbohydrates for the supply of metabolizable energy. Such efficient microbial digestion is not developed in humans and most of the simple stomached animals. Indeed dietary fibre is important for the maintenance of health. Dietary fibre includes cellulose, hemicellulose and lignin. Different gums, algal polysaccharides and pectic substances also contribute to dietary fibres. The diets containing very low percentage of fibrous substances are described low bulk diets. This situation results in high digestibility and undigested portion entering the colon is not adequate to stimulate optimum movements in colon. The colon becomes sluggish and bowel movements are irregular and decreased. Prolonged starvation and parentral feeding in sick animals whcih is results in atroply of the mucosa of the colon of the animal. This can be corrected by placing pectic substances in the colon. The lowered colon movements cause digestive disturbances and associated health problems. In humans, it has been observed that people consuming larger proportion of dietary fibre by eating fibrous foods, vegetables and fruits have low incidence of ailments like diverticulitis, cancer of the colon, diabetes mellitus and coronary artery diseases. However, such relationship between dietary fibre and such diseases needs further exploration for producing clear picture.

7

Proteins and Other Nitrogenous Substances of Nutritional Significance

Proteins are nitrogenous organic compounds and essential components of the cells and the body. The proteins are essential structural and functional components. The existence of life is not possible in the absence of proteins. All cells synthesize proteins but there is a major difference between the plant cells and the animal cells. The plants are capable of synthesizing proteins from inorganic nitrogen, carbon dioxide and water in the medium of chlorophyll in the presence of light. The sunlight is the main source of energy for photosynthesis for the production of amino acids, proteins, carbohydrates, lipids and vitamins. On the other hand, animals need about 9–11 pre-formed amino acids known as essential or indispensible amino acids for the synthesis of proteins.

7.1

Nomenclature of Protein

A Dutch scientist G.J. Mudler (1838) invented certain organic compounds which were claimed most important of all the known organic compounds produced by the plants and animals (say all living creatures). At that time itself it was claimed that life is not possible without proteins on this earth. However, the name “protein” was suggested by a contemporary scientist Berzelius. The term has been derived from Greek word “protein” means to occupy the first place. This information has been provided in the book “Nutrition: The Chemistry of Life” by L.B. Mendel (1923) published at the Yale University Press, New Haven. The first report of such substance was published in 1838 in the book “The chemistry of Animal and Vegetable Physiology” by G.J. Mulder.

# The Author(s), under exclusive license to Springer Nature Singapore Pte Ltd. 2021 S. K. Saha, N. N. Pathak, Fundamentals of Animal Nutrition, https://doi.org/10.1007/978-981-15-9125-9_7

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7.2

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Proteins and Other Nitrogenous Substances of Nutritional Significance

Constituents (Elements of Proteins)

The universal component of proteins is nitrogen along with essential components carbon, hydrogen and oxygen. These four elements are the basic essential elements. The three elements other than nitrogen are also the essential constituents of carbohydrates and fats. Large numbers of nitrogenous compounds form the protein Kingdom and many special proteins contain other elements in addition to common nitrogen, carbon, hydrogen and oxygen (Table 7.1).

7.3 1. 2. 3. 4. 5. 6. 7. 8. 9. 10.

7.4

Main Functions of Proteins Maintenance of characteristic shape of the body, tissues and cells. Main component of connective tissues and their functions. Proteins are constituents of cell, cell membranes and organelles of the cell. All enzymes are proteins and thus the metabolic functions of the enzymes. Many hormones like insulin are proteins. Proteins are carriers of many nutrients like iron, calcium and fat soluble vitamins, etc. Contractile proteins (actin and myosin) are essential for muscle contractions. Protective functions of immunoproteins against diseases. Maintenance of homoeostasis by blood proteins. Proteins are constituents of genetic units.

Limitations of Average Nitrogen Content in Intact Natural Proteins

Nitrogen content in various proteins of different foods/feeds differs from 15.5 to 18.9 percent on dry matter basis (Table 7.2). During the standardization of proximate principles at Weende in Germany, Hennenberg and Stohman averaged the nitrogen Table 7.1 Elements of protein molecules

Elements A. Common elements or basic components Carbon (C) Hydrogen (H2) Nitrogen (N) Oxygen (O2) B. Elements of specific proteins Phosphorus (P) Sulphur (S) Iron (Fe) Iodine (I) Cobalt (Co)

Percentage content 51.0–55.0 6.5–7.3 15.5–18.9 21.5–23.5 0.0–1.5 0.5–2.0 0.334–1.336 0.500 or so 4.5

7.5 True Protein Vis-à-Vis Crude Protein

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Table 7.2 Actual total nitrogen (N) content in some of the foods and respective factor for crude protein (CP) estimation on dry matter (DM) basis N content on DM basis Protein source (%) A. Animal protein foods Cow milk 15.5 Mixed milk 15.7 Meat, fish, 16.0 eggs B. Vegetable protein sources Maize grain 16.0 Wheat grain 17.2 Wheat flour 17.5 Cotton seed 18.9 Soybeans 17.5

Conversion factor for CP

CP values as per Actual 6.25 factor

6.452 6.37 6.25

96.875 98.125 100

100 100 100

6.25 5.814 5.714 5.29 5.74

100 107.50 109.38 118.13 109.38

100 100 100 100 100

content in the protein which worked out 16%. Therefore, from the 16% value of nitrogen content a factor 6.25 (100/16) emerged for the calculation of crude protein i.e. NX6.25. This factor is still used for the calculation of proteins and crude protein contents of foodstuffs. In the proximate analysis, nitrogen content is estimated in the foods/feeds for protein estimation which includes nitrogen of non-protein constituents. The science of nutrition has progressed and grow significantly during the past over one and quarter century and it will more appropriate to determine the actual value of nitrogen content in different foods and use actual factors for conversion of nitrogen content into crude protein. Protein nutrition of simple stomached as well as omnivorous animals including humans and carnivorous has advanced towards more new findings and now it is based on not only the protein content of the feeds but also the amino acids composition of the feeds protein is an essential and matters for the optimum functions during the different phases of life cycle (growth, pregnancy, lactation, body coat fibre, feathers and antlers, etc.). However, herbivorous animals are capable of efficient utilization of not only the non-protein nitrogen (NPN) compounds of natural feeds but also the NPN chemical by virtue of microbial symbiotic inhabitants in specialized segments of the alimentary canal of different species (Table 7.3).

7.5

True Protein Vis-à-Vis Crude Protein

All nitrogenous compounds of a feed are not proteins. The nitrogenous compounds other than true proteins are amino acids, urea, nitrates and nitrites, etc., and together these are called non-protein nitrogen (NPN). In proximate analysis total nitrogen content of foods estimated and converted into crude protein (CP) by multipling with a factor 6.25. Thus, CP value of foods/feeds is always higher than the value of true protein (TP).

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Table 7.3 Main sites of microbial digestion (fermentation) of some mammalian and avian species Class and main site of fermentation Species A. Foregut or pre-gastric fermentation 1. Ruminants and Bovine, ovine, caprine, pseudoruminants camelids 2. Non-ruminant Colombine monkey, herbivorous Kangaroo, Quokka Wallaby B. Post-gastric fermentation 1. Caecal Rabbit, hare, capybara fermentation lagomorphs 2. Colonic Equine (sacculated colon) 3. Colonic (a) Swine (unsacculated colon) (b) Homosapians (c) Caninesa (d) Felinesa a

Main natural foods Herbages. Capable of protein synthesis from NPN like urea Leaves, fruits, flowers, kernels

Herbages

Herbages Omnivorous Carnivorous Carnivorous

Domestication has made omnivorous

Although, all animals possessing well developed microbial fermentation segments in alimentary canal are capable of utilizing urea and other NPN compounds for the synthesis of amino acids and proteins but these are used only in the diets of ruminant and pseudoruminant animals. Due to pre-gastric location of fermentation vats in the ruminants there is little scope of ammonia (urea) toxicity on balanced feeding alongwith easily fermentable carbohydrates like molasses, starchy grains and starchy tubes and roots.

7.6

Structure of Proteins

The proteins are highly variable nitrogenous chemical constituents of the living cells and they are evolved for specific physiological functions in the body. The structures of proteins depend on various factors like number of amino acids, sequence of amino acids and presence of non-protein elements and compounds, etc. Normally four types of protein structures based on the linkages of the peptides are (1) primary structure, (2) secondary structure (3) tertiary structure and (4) quarternary structure. 1. Primary structure of proteins: These are straight long chains of amino acids linked with polypeptide bonds. The sequence of linkages for the formation of protein molecules is presented as follows:

7.7 Classification of Proteins on the Basis of Chemical and Structural Forms

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2. Secondary structure of proteins: The secondary structure of protein is different from the primary structure due to formation of hydrogen bonds immuno group and carboxyl group (C¼O) of the adjacent amino acids 3. Tertiary structure of proteins: In this type of structure R group of amino acids residues interact with the secondary structure resulting in the folding of protein molecule. 4. Quaternary structure of proteins: Protein molecules made up of more than one polypeptide chains acquire quaternary structure. The structure is maintained by hydrogen bonds and salt or electrostatic bonds formed between amino acid residues on the surface of polypeptides chains.

7.7

Classification of Proteins on the Basis of Chemical and Structural Forms

Since there is a great variations in the chemical and structural forms of proteins, a widely accepted classification was suggested in 1908. The two major groups are simple proteins and conjugated proteins. 1. Simple proteins: These are the proteins made up of only polypeptides, the products of polymerization of only amino acids. The amino acids are linked by peptide bonds. The common examples of simple protein are albumins, globulins, glutelins, histones, protamins, albuminoids and a few proteins soluble in alcohol. These are further classified into two subgroups of (a) globular proteins and (b) fibrous proteins on the basis of chemical composition, solubility and structure. Globular proteins These are made up of compact form of polypeptides composed of only amino acids. Globular proteins are soluble in water and aqueous saline. These are found in the following four chemical forms.

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a. Albumins: These are water soluble proteins of blood, milk, eggs and some herbages. Albumins coagulate on heating and turns colloidal on dissolving in water. These are used for the transportation of lipids and metals across the wall of intestines. The common examples of albumins are the ovalbumin of egg white, blood albumin and lactalbumin in milk. b. Globulins: These are the parts of globular proteins soluble in dilute salt solution. Globulins are found in three forms known as alpha (α), beta (β) and gamma (γ) globulins. The last one is associated with the development of defence systems against harmful foreign materials (pathogenic microorganisms or any other harmful substances). The form is known as immunoglobulins. Colostrum is rich in immunoglobulins and transferred to new born through colostrum feeding. The immunoglobulin molecules are transported into the body by the process of pinocytosis. c. Histones: These are globular proteins of nucleus and present in deoxyribonucleic acid (DNA) molecule. The histones are insoluble in water but soluble in milk salt solution. These do not coagulate on heating. The main compounds of hydrolysates are amino acids-arginine and lysine. d. Protamines: These are proteins of small molecules also present in the nucleus. The main constituent amino acid of protamine is arginine. The tryptophane, tysosine and sulphur containing amino acids are not found in the protamines. Fibrous Proteins These are made up of filaments formed of protein molecules, which are insoluble in water and highly resistant to enzyme action. The filaments are composed of elongated cells. The fibrous cells provide shape and strength to organs and finally the body construction as per the gene coding. Few common examples of fibrous proteins are the collagens, elastins, keratins, myosins and fibrin. a. Collagens: The fibrous proteins forming the connective tissues and also the proteinous matrix of bones and teeth are collagens. The collagens of bones are also known as ossein. The other tissues formed by collagens are the ligaments, tendons and skin (integument). The share of collagens is about 30 percent of the total proteins of the animal body tissues. Ascorbic acid (vitamin C) is essential for the synthesis of hydroxyproline from proline by the process of hydroxylation. The deficiency of vitamin C causes disorders of connective tissues, bleeding from gums and scaly skin. The collagens are converted into gelatins on boiling. Gelatin is more digestible than the collagens because solubility is increased on boiling. b. Elastins: These are constituents of ligaments, tendons and walls of arteries and veins. The name denotes the highly flexible nature of this protein. The elastins are also present with collagans in many tissues. Main amino acid constituents of elastins are alanine, glycine and lysine provides characteristic of retaining original shape of connective tissue after the removal of strain. Unlike collagens the elastins are not converted to gelatins on boiling. c. Keratins: Two types of keratins, i.e. alpha (α) and beta (β) keratins are found in the natural products. These are rich in sulphur containing amino acids. Alpha keratins are the components of wool and hairs, and beta keratins are largely

7.7 Classification of Proteins on the Basis of Chemical and Structural Forms

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present in feathers, beak, nails, hooves, horns and quills of porcupine. The constituent amino acid cysteine is synthesized from the another sulphur amino acid, methionine. d. Actinomyosin: This is produced by two contractile proteins-actin and myosin. Actinomyosin is used for the formation of striated muscles. e. Fibrin: It is formed from plasma protein, fibrinogen. The soluble fibrinogen of plasma is transformed into insoluble fibrin on reaction with thrombin. Fibrin is required for the clotting of blood. 2. Conjugated proteins: The proteins containing a non-protein moiety in the polypeptide chain of amino acids are known as conjugated proteins. The non-protein prosthetic group may be a sugars, lipids, minerals, pigments and nucleic acid etc. in the cojugated protein. The conjugated proteins are normally identified on the basis of their prosthetic groups, viz. glycoproteins, lipoproteins, phosphoproteins, chromoproteins, metalloproteins and nucleoproteins. a. Glycoproteins: In these proteins prosthetic group is a carbohydrate. The prosthetic group is one or more heteroglycans containing a hexosamine. The hexosamine moiety is galactosamine or glucosamine or both. In some of the glycoproteins other additional sugars like galactose and mannose may also be found. The glycoproteins are constituents of mucous secreted by mucous membranes for lubrication in different parts of the body. The major constituent of egg white (egg albumin) is a glycoprotein-a deposit of nutrients (proteinalbumin and carbohydrate) for the nourishment of developing embryo during incubation period. b. Lipoproteins: In these protein molecules the conjugating prosthetic group is a lipid. The common conjugating lipids are triacylglycerols and cholesterol. These are main constituents of cell membranes. These are main constituents of cell membranes. In these chemical forms lipids are transported in blood circulation to target tissues, where these are either oxidized for energy production or stored. The lipoproteins are further divided into five sub-classes on the basis of increasing density. There are (a) chylomicrons, (b) very long density lipoproteins (VLDL), (c) low density lipoproteins (LDL), (d) intermediate density lipo- proteins (IDL) and (e) high density lipoproteins (HDL). c. Phosphoproteins: The prosthetic group of these proteins is a phosphate moiety. Classical examples are the caseins in milk and phosvitin in egg yolk. The casings are produced by the phosphorylation of serine and threonine in the mammary glands. d. Chromoproteins: The prosthetic group of these proteins is a pigment which conjugate in the form of a phosphate of riboflavin like flavin mononucleotide (FMN) or flavin adenine dinucleotide (FAD). These flavoproteins are involved in biochemical reactions in the body requiring transportation of hydrogen. These are actively involved in the metabolism of carbohydrates and proteins (more specifically the amino acids).

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e. Metalloproteins: The proteins containing a metal or metal containing moiety as prosthetic group are the metalloproteins. Some of the examples are iron in haemoglobin, myoglobin and cytochromes, and copper in ceruloplasmin. Some groups include metalloproteins with chromoproteins due to formation of coloured molecules. Likewise proteins containing “haeme” (an iron containing prosthetic group) are also known as haemoproteins. f. Nucleo-proteins: The proteins containing nucleic acids as prosthetic group are called nucleoproteins like ribosomes. The nucleic acid is liberated on the hydrolysis of nucleoproteins.

Derived Proteins These are nitrogenous compounds obtained from the alternation and cleavage of natural proteins, which possess functional properties. Degradation of proteins may be caused by physical, chemical or biological factors like heat, alkalies acids and enzymes, etc. The degradation products of natural proteins are (a) primary derivatives like coagulated proteins, metaproteins and proteins (ii) the secondary derivatives are peptides, peptones and proteoses. The ultimate functional nitrogenous derivatives of proteins are the amino acids. The term “derived protein” has been now excluded and now it is a history.

7.8

Classificiation of proteins on the basis of physiological and nutritional roles

The name protein itself provides enough information regarding their roles in the living organisms. On the basis of specific and defined functions the proteins are classified into the following nine categories. 1. Structural proteins: These are mostly fibrous proteins involved in the maintenance of characteristic shape of organs and body. These are collagens, elastins, keratins, fibrin and actinomyosins. 2. Defence or protective proteins: These are proteins providing protection to body against clinical changes and injuries. Some of the examples are globulins (immunolglobulins) in colostrum, antibodies in vaccines, and fibrinogen and thrombin in blood. 3. Enzymes: These are mostly conjugated proteins possessing catalytic properties and play very important roles in the body, particularly in the digestion and metabolism of nutrients. The common examples are lipases, proteases, glucosidase, transaminases, etc. 4. Hormones or regulatory proteins: Some of the hormones are proteins like insulin is a true protein and glucagon is a derived protein. Others are tryroprotein releasing hormone, vasopressin, oxytocin, calcitonin, growth hormone and

7.9 Classification of Proteins for the Nutrition of Ruminants and Other Herbivorous. . .

5.

6.

7.

8.

9.

73

prolactin, etc. These are also known as regulatory proteins due to their role in the regulation of physiological functions in the body. Transport proteins: These are carriers of substances in the body. Albumin transports fatty acids. Haemoglobin and myoglobin are the carriers of oxygen to cells from the lungs and carbon dioxide from cells to lungs for exhalation. Contractile proteins: The myofibrils, constituents of muscle fibres are the thread like structures made up of elongated proteins and possess contractile property. These constitute 80–85% of the cell contents of skeletal muscles. Some of the proteins of myofibrils are myosin, actin, tropomyosin, troponin and many others. These are also called motile proteins. Storage proteins: These constitute greater proportion of all kinds of proteins in the body. These proteins are used by the subject itself or other persons (subjects) consuming the storage proteins. Some of the examples of storage proteins are the eggs of avian and reptile species that are used for nutrients supply by the developing embryos during the incubation period of fertilized eggs. The eggs of many avian species and few reptile species are also consumed by humans and other animals for nutrients supply particularly the supply of nutritious balanced proteins. Milk is another example of storage proteins of high nutritional value. Different amounts of proteins are also stored in the oil seeds, pulses, grains and other foods of plant origin. Storage proteins are mostly nutrient proteins and constitute significant proportion of diets of man and animals. Toxic proteins: A good number of proteins synthesized and stored by some animal, microbial, fungal and plant species are poisonous for humans and animals. Some are also fatal. A few examples of toxic proteins are lecithins, abrin, reserpine and snake venom. Miscellaneous proteins: There are still many unclassified proteins in the natural products like anti-freezing protein in the blood of fishes and other animals of arctic zone. Another proteinous substance present in a plant of Africa “monellin” is a sweet in taste. These appears to be good scope of its use as a sweetener for patients and other purposes.

7.9

Classification of Proteins for the Nutrition of Ruminants and Other Herbivorous Animals

The ruminants and almost all herbivorous animals possess modified alimentary tract enlarged for the storage of large quantity of bulky feeds of plant origin and also for providing optimum environment for establishment, growth and functions of useful symbiotic microorganisms. The sites of microbial activities for nutritional supplies to host are (a) pregastric in the ruminants and pseudoruminants, and post-gastric in equines, lagomorphs and many other herbivorous species. The symbiotic microbes particularly the bacteria are capable of degrading the dietary proteins to ammonia and resynthesizing transformed microbial proteins. All dietary proteins are not degraded in the rumen and escape to small intestine for enzymic digestion along

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with the digestion of microbial protein (microbial cells). On this basis dietary intact proteins are classified into (1) rumen degradable protein (RDP) and (2) rumen undegradable protein (UDP). The ruminants are also capable of utilizing ammonia nitrogen liberated from the hydrolysis of rumen soluble dietary proteins and non-protein nitrogenous (NPN) naturally compounds present in the feeds or supplemented as urea, ammonium sulphate, etc. Therefore, the protein sources for ruminants may be classified as: 1. Intact proteins: These are natural proteins in the feeds. Some parts of these protein are degraded in the rumen by the action of enzymes produced by the ruminal microorganisms. The proteins are further classified into: a. Rumen degradable protein (RDP): This is the portion of dietary protein which is fermented by ruminal microorganisms to peptides, amino acids and ammonia. Part of the ammonia is utilized by the rumen microorganisms for the resynthesis of microbial cells (proteins) that are digested in the small intestine and available to host for physiological protein requirements. The composition of microbial protein is largely different from the RDP fraction of dietary intact proteins. The quality of microbial protein may improve if the quality of RDP is poor and vice versa may also occur. b. Rumen undegradable protein (UDP): The portion of intact protein that does not ferment and degraded by the ruminal microbial activities is known as UDP. This portion of intact protein retains its structural amino acids constitution and digested in small intestine as in case of simple stomached animals.

7.10

Non-Protein Nitrogenous (NPN) Compounds as Sources of Protein Supply in Ruminants and Pseudoruminants

Once the rumen is fully developed and inhabited by natural beneficial families of microorganisms comprising of bacteria, protozoa, fungi and specialized microorganisms archaea, it is capable of utilizing NPN compounds like urea and ammonium salts for the synthesis of amino acids and proteins. These proteinous microorganisms also known as microbial proteins are digested in small intestine like a common protein supplement. The ruminant animal can maintain optimum health and production on nitrogen free complete feed containing NPN (urea or ammonium salts) compound as per the requirement. Since, most of the chemical NPN are rapidly hydrolysed in the rumen, their feeding is regulated for increasing nitrogen utilization efficiency and preventing ammonia toxicity.

7.11

Other Nitrogenous Compounds in the Body

The other nitrogenous compounds present in the animals and plants are the nucleic acids, amines, amides, nitrates, nitrites and alkaloids.

7.11

Other Nitrogenous Compounds in the Body

75

1. Nucleic acids: These are large molecule nitrogenous compounds that store the genetic information in living cells. These genetic information are utilized for the synthesis of proteins (high molecular weight polypeptides). The name nucleic acid was given due to their first identification in the nucleus of living cells. The original name was Nucleinstoffe (it was coined by Miescher in 1870). The constituents of nucleic acids are (1) basic nitrogenous compounds-purine and pyrimidine, (2) pentose sugars—ribose and deoxyribose and (3) phosphoric acid. Thus, the nucleic acids are large size molecules of glycophosphoproteins. a. Basic Nitrogenous Compounds: Main basic nitrogenous compounds of nucleic acids are (a) pyrimidine and (b) purine

Pyrimidine Derivatives The main pyrimidines of nutritional and physiological importance present in nucleic acids are (1) cytosine, (2) thymine and (3) uracil.

Purine Derivatives The main purines of nutritional and physiological importance in nucleic acids are (a) adenine and (b) guanine

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Nucleosides and Nucleotides The chemical compounds formed from the reaction of a purine or a pyrimidine base with a pentose sugar—ribose or deoxyribose are known as nucleosides. The esterification of nucleosides with phosphoric acid produces nucleotides (Table 7.4). Nucleic Acids Two types of nucleic acid are (1) ribonucleic acid (RNA) and (2) deoxyribonucleic acid (DNA). Both nucleic acids are the polymerization products (polynucleotides) of their respective nucleotides. The molecular weight of nucleic acids is very high measuring millions Kda. The nucleotides are arranged in a definite pattern in the DNA molecule forming a double strand helix. Each strand of helix is formed of an alternate unit of deoxyribose and phosphate. To each sugar unit one of the four pyrimidine (cytosine and thymine) and purine (adenine and guanine) base is bonded. The sequence of bases along the DNA strand of helix carries the genetic information. The synthesis of DNA and RNA occurs in the liver. The DNA once synthesized remains stable in the life, whereas RNA remains in dynamic equilibrium with the amino acid pool. Fate of Pyrimidine and Purine Bases The pyrimidine and purine bases are liberated on the metabolism of nucleotides. Part of these bases is again used for the synthesis of nucleosides, nucleotides and nucleic acids. A small quantity is excreted in urine unchanged. The remaining portion is

Table 7.4 Nucleosides, nucleotides and nucleic acids containing pyrimidine or purine bases Base A. Pyrimidine base (a) Cytosine (b) Thymine (c) Uracil B. Purine bases (a) Adenine (b) Guanine

Nucleosides

Nucleotides

Nucleic acids

(a) Cytidine (b) Deoxycytidine (a) Thymidine (b) Deoxythymidine Uridine

(a) Cytidylate (b) Deoxycytidylate (a) Thymidylate (b) Deoxythymidylate Uridylate

(a) RNA (b) DNA (a) RNA (b) DNA RNA

(a) Adenosine (b) Deoxyadenosine (a) Guanosine (b) Deoxyguanosine

(a) Adenylate (b) Deoxyadenylate (a) Guanylate (b) Deoxyguanylate

(a) RNA (b) DNA (a) RNA (b) DNA

7.11

Other Nitrogenous Compounds in the Body

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catabolized. The pyrimidines are catabolized to produce carbon dioxide and ammonia, and the purines are catabolized to produce uric acid. Functions of DNA and RNA The DNA molecules of a cell determine the structure of proteins depicted by amino acids sequence in the polypeptide chain. The RNA molecules, a sequence of nucleotides are also held by the DNA in that cell. These biological reactions are highly specific and controlled by DNA. All biological information of the functions of a cell are stored in the DNA of that cell. The RNA molecules possess the function of information storage and catalysis. Different groups of RNAs present in the cell have well defined specialized functions. The three main functional groups of RNAs are (1) messenger ribonucleic acid (mRNA), (2) transfer RNA (tRNA) and (3) ribosomal RNA (rRNA). Differences between DNA and RNA have been made in table. Deoxyribonucleic acid (DNA) 1. Sugar moiety is deoxyribose 2. DNA are stable molecules and live life long 3. DNAs are found in helix shape formed by two long strands of deoxynucleotides 4. DNA is the component of chromosomes 5. DNA stores all genetic information of that cell 6. DNA molecules contain thymine and other bases

Ribonucleic acid (RNA) Sugar moiety is ribose RNA live in dynamic equilibrium in animals acids pool Most RNA molecules are formed of single strand of ribonucleotides RNA is not a component of chromosomes Information stores of RNA is controlled by DNA RNA contains uracil in place of thymine

2. Amides: These are functional derivatives of amino acids and produced by the replacement of hydroxyl group of carbonyl moiety by the amino (NH2) group of ammonia. The amides are represented by a common formula R-C-NH2. Some amides like asparagine and glutamine are polar products of corresponding amino acids, i.e. aspastic acid and glutamic acid. These two amides are also considered as amino acids and present as constituents of proteins. Asparagine and glutamine are present in free form and actively participate in the transamination reactions. The other important amide, urea is the main end product of protein and proteinous compounds metabolism in the mammalian species. It has been also reported in some amphibian species and cartilaginous fishes. Many plants like some cereal grains, soybean, potatoes and green herbages also contain urea (figure). Uric acid is the metabolic end product of protein metabolism in the birds and reptiles. A small quantity is also produced in the homosapian species including human being from the metabolism of purines. The purines are produced from the metabolism of aspartate, glutamate and glycine. In the humans and some other primates part of uric acid is oxidized to allantoin.

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The animal species converting ammonia into uric acid as main end product of protein metabolism are known as uricotelic animals. These are birds and reptiles. Most of the aquatic animals excrete ammonium (NH4) ions and they are called ammonotelic animals. The teleost fishes (a kind of bonny fishes), protein metabolism produces allantoate as excretory end product.

3. Amines: The amines are produced from the decarboxylation of amino acids, viz. production of catecholamines (dopamine, norepinephrine and epinephrine) from tyrosine metabolism. These are basic compounds found in small quantity in anima tissues and most of the plants. Several species of microorganisms are capable of converting amino acids to amines, and in certain conditions the ruminal and silage microorganisms (dominated by clostridia) also produce amines from the amino acids (Table 7.5). Some of the amines like members of catecholamine are neurotransmitters. Some others like histamine are vasodilator and its excess secretion stimulated by allergens leads to acid secretion in the stomach resulting in acute acidosis. This

Table 7.5 Amino acids and their metabolite amines S. No. 1. 2. 3. 4. 5. 6. 7.

Amino acid Arginine Histidine Lysine Methionine Phenylalanine Tryptophane Tyrosine

Amine Putrescine Histamine Cadaverine Spermine, spermidine Phenylethylamine Tryptamine, epinephrine Dopamine, norepinephrine (Tyramine)

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Other Nitrogenous Compounds in the Body

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ultimately causes gastro-duodenal ulceration, if prolonged for several days. The odour of most of the amines is offensive. Some amines are also found in many fermented foods proceed from microbial culture. 4. Nitrates and Nitrites: These are harmful NPN compounds for the animals particularly the ruminants. These are intermediary metabolites in the sequence of amino acids and protein synthesis in plants. In the absence of light reactions remain incomplete resulting in the accumulation of these chemicals in the herbage. Fast growth, short day length and heavy dosing of nitrogenous fertilizers (urea) are the causes of nitrites and nitrates accumulation in herbages. Nitrates are not toxic but nitrites are highly toxic and effect is acute and fatal due to loss of oxygen transport due to formation of met-haemoglobin. Nitrates are quickly converted into nitrites by the ruminal and enteric microorganisms. 5. Toxic alkaloids (NPN compounds) in herbages: Many types of forage and other plants produce and store toxic alkaloids. In natural conditions most of the wild and feral herbivorous animals are able to identify toxic plants and also the stage of plant growth or part (S) of the plants containing toxic substances. However, this ability has been almost completely abolished due to domestication causing separation from the natural environment for very long period. Due to this reason domestic animals have almost lost the ability of identifying most of the toxic plants in nature. Some of the plants and their toxic alkaloids are presented in Table 7.6.

Table 7.6 Some plants containing toxic alkaloids S. No. 1. 2. 3. 4. 5. 6. 7. 8. 9. 10. 11. 12. 13. 14. 15. 16.

Common name Anabisis Caton bean Cinchona bark Dature Deadly nightshade Coca leaves Hemlock Mexican poppy Nux vomica Opium poppy Potato (green, sprouting) Regwort Rathi Rauvolfia Subabool Tobacco

Botanical name Anabasis aphylla Ricinus communis

Alkaloid Anabasine Ricinine Quinine

Stramonium datura

Papaver somniferum Solanum tuberosum Abrus tinctorius Rauwolfia serpentina Nicotiana tabacum

Atropine Cocaine Conine Mixed alkaloids Strychnine Morphine Solanine Jacobin Abrin Reserpine Mimosine Micotine

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Proteins and Other Nitrogenous Substances of Nutritional Significance

Molecular Weight and Number of Amino Acids in Some Protein Molecules

Most of the protein molecules are made up of 1–5 polypeptide chains of amino acids arranged in a gene controlled characteristic sequence for each type of proteins. The proteins are very high molecular weight organic compounds. These are structural and functional constituents of tissues. Some examples of molecular weight, number of amino acids and number of polypeptide chains are presented in Table 7.7. Protein molecules made up of two or more polypeptide chains are known as multisubmit proteins. The polypeptide chains of a multisubunit protein may be similar or different in amino acids sequence. The sub units of polypeptide chains in a multi sub units protein containing some identifiable sub-units (protomers) are identified as oligomeric proteins. An example of single polypeptide chain protein is cytochrome C (human). The haemoglobin has two identical polypeptide chains, each of alpha (α) and beta (β) chains linked by non-covalent effects. The percentage of small size amino acids is usually higher in the polypeptide chains of proteins.

7.13

Amino Acids Composition of Proteins

Simple proteins are made of a mixture of amino acids that liberate on hydrolysis. The hydrolysate thus obtained is a mixture of free alpha amino acids. However, number of an amino acid in the polypeptide chain may differ. The amino acid composition of Table 7.7 Molecular weight, amino acid residues and number of polypeptide chains Protein Insulin Insulin Cytochrome Ribonucleic A Lysozyme Lactalbumin Myoglobin Chymotrypsin Chymotrypsinogen Haemoglobin Serum albumin Immunoglobulin G Apolipoprotein B Glutamine dehydrogenase a

Approximate values

Source Bovine Human Human Bovine (pancreas) Egg albumin Milk Equine heart Bovine Bovine Human Human Human Human Bovine

Molecular weight (kDA) 5733 6000 13,000 13,700

Number of amino acids 51 84 104 124

Polypeptide chains 2 2 1 1

13,930 17,400 16,890 21,600 22,000 64,500 68,500 145,000 513,000 1,000,000

129 – 153 241 245 574 550a 1320 4636 8300

1 – 1 3 1 4 1 4 1 40a

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Amino Acids Composition of Proteins

81

chymotrypsinogen molecule of cattle and that of cytochrome C of human origin is presented in Table 7.8. The type and number of amino acids of a protein are constant but sequence of amino acids in the chain is considerably variable resulting in protein polymorphism in humans and animals. These variations may or may not affect the physiological functions. In the body tissues of animals (including humans) 50,000 to 100,000 or even more number of proteins are produced against only 3000 types of proteins in a cell of bacterium Escherichia coli.

Table 7.8 Amino acids composition of few proteins

Chymotrypsinogen Amino acids Number Percent A. Non-polar alliphatic amino acids Alanine 22 8.98 Glycine 23 9.39 Isoleucine 10 4.08 Leucine 19 7.755 Proline 9 3.67 Valine 23 9.39 Total 106 43.265 B. Non-polar aromatic amino acids Phenylalanine 6 2.45 Tryptophane 8 3.26 Tyrosine 4 1.633 Total 18 7.343 C. Polar unchanged amino acids Asparagine 15 6.12 Cysteine 10 4.08 Glutamine 10 4.08 Methionine 2 0.82 Serine 28 11.43 Threonine 23 9.39 Total 88 35.92 D. Polar positive charged amino acids Arginine 4 1.63 Histidine 2 0.815 Lysine 14 5.71 Total 20 8.155 E. Polar negative charged amino acids Aspartate 8 3.265 Glutamate 5 2.04 Total 13 5.305 Grand Total 245 100

Cytochrome C Number Percent 6 13 8 6 4 3 40

5.77 12.50 7.69 5.77 3.85 2.88 38.46

3 1 5 5

2.88 0.96 4.81 4.81

5 2 2 3 2 7 21

4.81 1.92 1.92 2.88 1.92 6.73 20.18

2 3 18 23

1.92 2.88 17.31 22.12

3 8 11 104

2.88 7.69 10.57 100

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Amino acids sequence of different types of proteins is different. The amino acids sequence in polypeptide chains of proteins governs the physiological functions. Occurrence of defective or altered sequence of amino acids in polypeptide chains of many proteins is not uncommon. These defective sequences in the polypeptide chains of proteins of human tissues have been found to be the aetiology of more than 1400 diseases of genetic origin. The functions of proteins are totally dependent on the sequence of amino acids in the molecule. There are very important segments of amino acids sequence in the chain which are responsible for characteristic functions of that proteins. An alternation in the sequence of such segments of protein may produce clinico-pathological conditions. The amino acids sequencing of tissue proteins of animals is expected to univeil many secrets of production and health status. The information may be used beneficially for genetic manipulations.

7.14

Amino Acids

The organic acids containing amino group (–NH2) in their molecules are known as amino acids. These are constituent units of proteins arranged in polypeptide chains linked by peptide bonds. Simple amino acids are composed of carbon, hydrogen, oxygen and nitrogen linked in such a manner to contain an amino (NH2) group and a carboxyl (–COOH) group in a molecule. These two active groups are bonded with the same carbon and may be represented by a common structure (Fig. 7.1).

7.14.1 Amino Acids of Animals and Plants Tissues Out of more than 300 known amino acids only 20 are naturally found in the tissues of animals and plants. The amino acids of higher animal and plant species are alpha (α) amino acids.

7.14.2 Identification of Amino Acids Different kinds of amino acids are identified on the basis of side chain and “R” group. Both of these have different sizes, structures and electric charge. These Fig. 7.1 Amino acid

NH2 ↑ R----C-------COOOH ↓ H

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Amino Acids

83

factors are responsible for difference in their solubility in water. The first carbon atom in the structure of amino acids has been designated alpha carbon and as the number of carbon atom increases in the chain, their designation becomes beta, gamma, delta, epsilon, zeta, etc. as per Greek letters in progressive order.

7.14.3 Normal, Primary or Standard Amino Acids Twenty amino acids involved in the synthesis of proteins and physiological functions in the animal body and higher plants are known as normal, primary or standard amino acids. These 20 normal amino acids have been given universally accepted abbreviations three letters and symbol single capital letter (Table 7.9). These amino acids have been further grouped into five categories on the basis of physical properties. The capital letters used as symbols are not necessarily the first letter of amino acids. These symbol letters are the outcome of agreement among a group of concerned scientists. Table 7.9 Standard amino acids, abbreviations, symbols

Amino acids Abbreviation Symbol A. Non-polar amino acids with aliphatic “R” group 1. Glycine Gly G 2. Alanine Ala A 3. Proline Pro P 4. Valine Val V 5. Isoleucine Ile I 6. Leucine Leu L B. Non-polar amino acids with aromatic “R” Group 1. Phenylalanine Phe F 2. Tyrosine Tyr Y 3. Tryptophane Try W C. Polar amino acids with unchanged “R” group 1. Serine Ser S 2. Theanine Thr T 3. Cystine Cys C 4. Asparagine Asn N 5. Glutamine Glu Q 6. Methionine Met M D. Polar amino acids with negative charged “R” group 1. Aspartic acid Asp D 2. Glutamic acid Glu E E. Polar amino acids with positive charged “R” group 1. Lysine Lys K 2. Histidine His H 3. Arginine Arg R

Group 75 89 115 117 131 131 165 181 204 105 119 121 132 146 149 133 147 146 155 174

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7.14.4 Classification of Amino Acids of Natural Proteins on Chemical Characteristics The twenty amino acids of natural proteins are classified as follows on the basis of chemical properties. 1. Aliphatic amino acids: All amino acids with cyclic or fatty properties are called aliphatic amino acids as shown in the following straight and branched chain structures. (a) NH2CH2COOH

(b) NH2-CH-COOH CH3

The aliphatic amino acids are further divided into the following four groups on the basis of chain length and sulphur content in the molecule. a. Mono-amino mono carboxylic acids: These are neutral aliphatic amino acids containing one amino group and one carboxylic group. The glycine, alanine and serine are sweet in taste and isoleucine, leucine, threonine and valine are flat taste or tasteless. b. Mono amino-dicarboxylic amino acids: Aliphatic amino acids containing one amino group and two carboxylic groups are acidic in reaction. The examples are aspartic acid and glutamic acid that contain negative (-) charged “R” groups. c. Diamino-monocarboxylic or basic amino acids: These contain two amino groups and one carboxylic group. Reaction of these amino acids is basic, viz. lysine and arginine. The taste of arginine is bitter.

Lysine (α,β diaminocaproic acid)

Arginine (α-amino-γ-guanidine valeric acid)

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Amino Acids

85

d. Sulphur containing amino acids: These amino acids contain a sulphur atom in their molecule. These amino acids are more important for fibrous proteins synthesis, viz. methionine and cysteine.

2. Aromatic amino acids: The amino acids containing a cyclic (ring) structure in their molecule and emitting characteristic aroma (odour) are known as aromatic amino acids. Examples are phenylalanine and tyrosine.

3. Heterocyclic amino acids: These are amino acids possessing pentagonal ring in their molecular structure, viz. proline, histidine and phenylalanine.

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a. Proline (α-pyrrolidine carboxylic acid)

b. Histidine (a-amino b-imidazole propionic acid)

c. Tryptophane (α-amino-β-indole propionic acid) 4. Iodine containing amino acids: The derivatives of tyrosine, triiodothyronine and tetraiodothyronine (thyroxine) are iodine containing amino acids. These are thyroid hormones and responsible for the regulation of iodine metabolism in the body.

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Amino Acids

87

7.14.5 Properties of Amino Acids 7.14.5.1 Physical Properties of Amino Acids 1. These are colourless crystalline nitrogenous organic compounds present in living animals and plants. 2. These are soluble in water, sparingly soluble in alcohol and insoluble in either. 3. These are readily ionized in aqueous solution and due to the presence of acid and basic ions, the reactions are both acidic and basic. Such property is known as amphoteric nature. The compounds liberating both anions and cations in aqueous solution are called zwitter ions. In German languages zwitter means hybrid. 4. Isoelectric pH or pH at which amino acids in aqueous solutions live in zwitter ionic form differ from different amino acids. At this pH behaviour of amino acid solution is electrically neutral and ions do not migrate to any electrode. The values of isoelectric pH of aqueous solutions of neutral amino acids vary between 4.8 and 6.3; for acidic amino acids 2.8 and 3.2; and for basic amino acids 7.6 and 10.8. 5. Buffer property of amino acids is due to amphoteric property in aqueous solution. 6. The alpha amino acids of proteins except glycine are optically active. The alpha carbon atom of optically active amino acids is asymmetrical and it is linked with four groups, viz. a carboxyl group, a “R” group, an amino group and a hydrogen atom. Such molecules can exist in two isomeric forms known as stereoisomers and because of their non-superimposable nature they are also called enantiomers as shown in figure.

7.14.5.2 Chemical Properties of Amino Acids The chemical properties of amino acids are influenced by carboxyl (–COOH) and amino (–NH2) groups in the molecule. Chemical Properties due to Carboxyl (–COOH) Group 1. Amino acids from esters on reaction with alcohols and salts with alkalies. 2. Reaction with ammonia produces amides, viz. aspartic acid + ammonia yields asparagine. 3. Hydroxyzine (NH3.NH2) is capable of breaking the peptide bonds for producing corresponding hydrazides.

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Chemical Properties Due to Amino Groups 1. Amino acids can form salts with acids. 2. Reaction of amino group with nitrous acid yields hydroxy acid and nitrogen is released. 3. Methylation may be possible. 4. Amino acids react together and form peptide chains which continue up to the synthesis of proteins in optimum conditions.

7.14.5.3 Essential or Indispensible Amino Acids Amino acids are the constituent units of proteins. All plants and most of the microorganisms particularly bacteria are capable of synthesizing amino acids from non-protein nitrogenous (NPN) compounds like nitrites, nitrates and urea, etc. Some of the bacteria like azotobacters, rhizobium, methylococcus and several other are capable of gaseous nitrogen fixing. Reduction of nitrogen to ammonium form is essential which is catalysed by the enzyme nitrogenase. Animals are unable to synthesize amino acids form nitrogen and non-amino nitrogenous compounds and require supply of amino acids and proteins in their diets for the synthesis of 20 amino acids of body proteins. The animals are not able to synthesize almost half of the amino acids essential for the formation of body proteins and require preformed for body protein synthesis. These amino acids are known as essential or indispensable amino acids. Essentially of ten amino acids for the normal growth and other physiological functions of animals was established by the classical studies of W.C. Rose using purified diets of 20 amino acids of proteins. The rats were experimental animals. The amino acids were fed in different combinations by eliminating one amino acid each time. Therefore, from these experiments 10 amino acids were found essential for rats. These are also essential for the growth of humans and others. These essential amino acids are arginine, histidine, isoleucine, leucine, methionine, phenylalanine, threonine, tryptophane and valine. Later on a group of researchers at the university of California added two more amino acids, glycine and tyrosine in the list of essential amino acids. The remaining (10 in some species 8) amino acid of 20 constituents of proteins are non-essential or dispensible amino acids and synthesized in animals from other amino acids. The essential amino acids are represented by single letter symbols A, H, I, L, M, P, T, T and V. These symbols were arranged in a name AVHILLMPTT. This code was synthesized by a group of students of Sir Archibald including Vivan Hill (AVHILL) who joined politics and became member of parliament (MP) of Torry Team (TT). The merger of AVHILL+MP+TT became AVHILLMPTT to represent to essential amino acids for most of the animals.

7.14

Amino Acids

89

Table 7.10 Essential amino acids for mammals and birds in general S. No. 1. 2. 3. 4. 5. 6. 7. 8. 9. 10.

Essential amino acids Mammals Birds Arginine Arginine Histidine Histidine Isoleucine Isoleucine Leucine Leucine Lysine Lysine Methionine Methionine Phenylalanine Phenylalanine Threonine Threonine Tryptophane Tryptophane

Non-essential amino acids Mammals Birds Glycine Essential Serine Serine Cystine Cystine Tyrosine Essential Aspartic acid Aspartic acid Glutamic acid Glutamic acid Proline Proline Hydroxyproline Hydroxyproline Citrulline Citrulline

Essential Amino Acids for mammals and birds The names of essential (indispensible) amino acids for most of the mammalian and avian species are listed in Table 7.10. Some Acceptions of Essential Amino Acids The essentiality of some of the designated essential amino acids changes to certain extent on the availability of other sources and limited synthesis in the body of fast growing and high producing (milk) animals and some observe reasons. 1. Part of methionine supply can be made by cysteine in the diet. Similarly phenylalanine and tyrosine, and glycine and serine are complementary in some conditions. 2. Glycine and tyrosine are essential for poultry birds. 3. Taurine and argine are essential in the diets of felinves (cat, tiger, lion, etc.) 4. Dietary arginine supply is required for optimum growth of fast growing pigs. 5. Arginine and histidine are essential for infant and growing humans but not for the adults. 6. Ruminal microorganisms are capable of synthesizing all the essential and non-essential amino acids even from the NPN source like urea provided organic carbon source and elements like sulphur are available. However, for supplying the requirements of very fast growing and high milk yielding ruminants dietary supplementation of some of the essential amino acids is necessary. Amino Acids for Poultry Enormous development has been made in growth and egg production of chicken and some other poultry birds. This has significantly affected the protein requirement and protein quality supply in balanced diets for meeting requirements of optimum production. Now amino acids of poultry diets are classified into essential, critical, limiting and non-essential amino acids (Table 7.11).

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Table 7.11 Types of amino acids in poultry diets Essential amino acids Lysine Methionine Tryptophane Theorinine Arginine Isoleucine Leucine Valine Histidine Phenylalanine Glycine Tyrosine

7.15

Critical amino acids Lysine Methionine Tryptophane Theorinine Arginine Isoleucine – – – – – –

Limiting amino acids Lysine Methionine Tryptophane – – – – – – – – –

Non-essential amino acids Alanine Aspartic acid Glutamic acid Proline Serine Hydroxyproline – – – – – –

Chemical Structures and Compensatory Properties of Amino Acids in Animal Nutrition

The amino acids in animal and plant proteins are mostly produced in the L-isomer form which are more efficiently utilized than their D-isomer form. However, methionine metabolism of L- and D- isomers of methionine is equally efficient in growing young pigs. Contrary to this efficiency of utilization of D-tryptophane in growing pigs is only about 60–70% of L-tryptophane. D-isomers of lysine and threonine are not utilized by any species of domestic animals. Cystine is synthesized in the animal body only from methionine but methionine is not synthesized. Therefore, almost half of the requirement of methionine + cystine of domestic simple stomached animals and 75% that of humans can be supplied by dietary cystine. Similarly dietary tyrosine can meet 30–50% requirement of phenylalanine of starting chicken, about one-third requirement of growing pigs and 75% requirement of growing rats and adult humans. Tyrosine can be synthesized from dietary phenylalanine but phenylalanine is not synthesized from tyrosine.

7.16

Utilization of Amino Acids (Proteins) in the Body of Animals

The utilization of amino acids, the digested and smallest units of proteins depends on the supply of metabolizable energy. The excess intake of proteins (amino acids) is not beneficial and puts addition load on metabolism and wastage of energy in excess nitrogen excretion in the form of urea in urine. Excess protein is deaminated and utilized for the production of glucose by gluconeogenesis.

7.18

7.17

Complete and Incomplete Proteins

91

Glucogenic and Ketogenic Amino Acids

After absorption in the body pool greater percentage of amino acids is utilized for the synthesis of body proteins. A part of amino acids intake is utilized for the production of hexose sugars. All the amino acids except leucine are glucogenic (glucose producing). The leucine is ketogenic. The lysine, isoleucine, threonine, phenylalanine, tryptophane and tyrosine are both glucogenic and ketogenic. Ketogenic amino acids produce acetyl-coA which is converted to acetoacetic acid (a ketone body). Leucine is only true ketogenic amino acids out of the 20 amino acids of the proteins in animal body.

7.18

Complete and Incomplete Proteins

These terminologies are used for the depiction of protein quality in applied human nutrition and dietetics. The ability of different kinds of proteinous foods to meet the requirements for normal physiological functions has been used for the classification of food proteins into (1) complete proteins, (2) partially complete proteins and (3) incomplete proteins or proteinous foods. 1. Complete proteins: The proteinous foods containing all the essential amino acids required for growth, pregnancy, lactation and maintenance of health are called complete proteins. The biological value and amino acids score of these proteinous foods are very high. This class includes milk, meat, fishes, lobsters, crab, eggs and other proteinous foods of animal origin. 2. Partially complete proteins: These proteins are capable of supplying essential amino acids for the maintenance of adult persons but not sufficient and will not be able to fullfil the protein requirement for growing children, pregnant and nursing ladies and healing of wounds. The common sources of partially incomplete proteins are cereal grains, pulses and oil seeds. The amino acids composition of these plant (vegetable) proteins are highly variable and differes from source to source. Fixing of few food grains, pulses and oilseeds or oilseed extractions has been found nutritionally useful. Pulses are good sources of proteins and should be preferably used as a mixture of 4, 5 or more in the diets. Flour of oil seed meals like soybean, groundnut, sesame, linseed and sunflower, etc. may also be used for protein enrichment of wheat flour and other cereal flours. 3. Incomplete proteins: These are very poor sources of protein and available essential amino acids. These are normally not included in the diets of humans. The zein extracted from maize kernels and gelatin from animal tissues are the two adultrants of foods and protein value of these two foods are almost zero.

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Proteins and Other Nitrogenous Substances of Nutritional Significance

Need of Complete Protein Supplementation in the Diets of True Vegetarian People

Foods of plant sources like cereal grains, leguminous seeds (pulses), vegetables, oilseeds and tubers are generally deficient in four essential amino acids. These are lysine, methionine, threonine and tryptophane. The proteins of these foods are not balanced to meet the essential amino acids for growth, pregnancy and lactation. Therefore, it is necessary to use foods of animal origin like milk, meat, eggs and fishes, etc. for balancing the physiological requirements of essential amino acids.

7.20

Non-Protein Nitrogen (NPN) Sources for Protein Supply of Ruminants

The ruminants are bestowed with ability of utilizing non-protein nitrogen (NPN) compounds for the synthesis of amino acids for their own requirements under native state of evolution. This is possible by diversified groups of bacteria, archaea, protozoa, yeasts and moulds which live under multalism state of symbiosis in the rumen. Rumen is a pregastric enlargement of alimentary canal for holding large volume of bulky fibrous herbaceous feeds rich in cellulosic compounds. The environment at pH 6.5– 6.9 for most of the time is quite congenial for the functions and proliferation of ruminal microorganisms. NPN substances are used for the synthesis of amino acids of microbial cells, which are digested as protein source in small intestine.

8

Lipids

Lipids are the triacylglycerols of fatty acids, their derivatives, complexes and fat soluble compounds. These include different groups of organic substances soluble in organic solvents like ether, chloroform and hexane, etc., but insoluble in water. Lipids are one of the important constituent groups of plants and animals body. Triglycerides (triacylglycerols) constitute the largest component (more than 90%) of the total lipids in the body. The other constituents of lipids include cholesterol, cholesterol esters, sterols, phospholipids, glycolipids, fat soluble pigments and several other associated compounds like terpenes, waxes and cerebrosides, etc. Fat soluble vitamins A, D, E and K are also included in the large family of lipids.

8.1

Functions

The functions of fats, fatty acids and non-fat lipids are different and the fuction of the different fat compound may also differ significantly. Some of the general functions of active lipids or metabolizable lipids may be listed as follows: 1. Most of the lipids specially fats are the richest sources of energy and found stored in the plant and animal tissues. The fat contain about 2.25 times more dietary energy than the carbohydrates and available energy from proteins. 2. The lipid are the functional constituents of biological membranes. 3. Some lipids are substrate carriers in enzyme reactions during metabolism. 4. The Lipid are also carriers for the transportation of electrons. 5. Some lipids are structural components of cells and some others are stored as depots fat. 6. The subcutaneous fat layer in animals is an insulator for providing protection from cold and mild blows. 7. The stored fat in some warm blooded animal species is used for the maintenance of body temperature. # The Author(s), under exclusive license to Springer Nature Singapore Pte Ltd. 2021 S. K. Saha, N. N. Pathak, Fundamentals of Animal Nutrition, https://doi.org/10.1007/978-981-15-9125-9_8

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8 Lipids

8. In young calves, special deposit of adipose tissue on shoulders and abdomen (known as brown fat) in active cells provides heat for maintenance in emergency.

8.2

Classification of Lipids

The following five methods have been frequently used for the classification of lipids. 1. 2. 3. 4. 5.

The classification on the basis of glycerol based and non-glycerol based lipids. The classification on the basis of saponification. The classification on the basis of main sources. The classification in different chemical groups. The classification on the basis of chemical nature.

The first method of classification is now widely used for nutritional purpose. Brief informations are provided for showing the changes in the classification systems of lipids.

8.2.1

Classification of Lipids on the Basis of Glycerol and Non-glycerol Lipid Compounds

In this system the lipids are first divided into two broad groups of glycerol based and non-glycerol based compounds. In the plants and animals largest proportion of lipids are glycerol based which are generally condensed sources of high energy molecules like fats (including oils). The elaborate classification is presented in Fig. 8.1. Steps 1. Initiation Presence of air Fat molecules

Free radicals (O) Light, heat, moisture, microbial activities

Steps 2. Acceleration Oxygen Free radicals

Peroxides H2O2 + Free radical + short chain fatty acids

Peroxide + fat Steps 3. Termination of reaction End products

Aldehydes, ketones, sort chain fatty acids and others

Fig. 8.1 Steps of auto-oxidation of fats

8.2 Classification of Lipids

8.2.2

95

Lipids Classification on the Basis of Saponification

The lipids hydrolysed on boiling with alkali into glycerol and soap are termed as saponifiable and others as non-saponifiable lipids.

8.2.3

Lipids Classfication on the Basis of their Main Sources

Plants and animals are the two main groups of lipids supply in the nature. These lipids are normally classified on the following pattern. 1. Lipids of plant origin or vegetable lipids: These are either structural or storage lipids. a. Structural plant lipids: These are lipids of membranes and protective layer on the surface. The membrane lipids are glycolipids (up to 50%) and phospholipids. These are found in plasma membranes, mitochondria and endoplasmic reticulum. The protective layer of lipids is waxes present in the different amounts in different parts of the plants (mainly the leaves surface). Small fractions of fatty acids and cutin are also present in the surface lipids. b. Storage lipids in plants: These are mostly oils stored in the seeds and fruits and sometimes also in the main body of the plants of some species. Fats of most of the vegetable sources are rich in unsaturated fatty acids. Higher percentage of saturated fatty acids. Higher percentage of saturated fatty acids are present in few plant species like fats of mahua seed, sal seed and cocoa butter. The fats found in liquid at room temperature are generally called oils. 2. Lipids of animal origin: Similar to plants these are also structural and storage lipids. a. Structural lipids of animal tissues: These are constituents of membranes and found less than 1 (0.5–1.0) percent except the live parenchyma (2–3%). The structural lipids in animal tissues also include cholesterol and cholesterol esters together making less than 0.09 (0.06–0.09) percent of the membranes of muscles and adipose tissues. b. Storage lipids in animal body: These are mostly present in the fat depots like subcutaneous tissue, peritoneum and peri-renal membrane. The stored fats in animal body are present in anhydrous form. Contrary to fats, glycogen (carbohydrate) is present in hydrated form. Complete oxidation of 1 g stored dry fat yields 9.32 kcal or 39 kJ gross energy against 4.06 kcal or 17 kJ gross energy from the oxidation of 1 g stored glycogen in the body. 3. Lipids classification as used in human nutrition: A simple method of lipid classification is used in nutrition and dietetics. It gives some indications of relationship with health of humans and animals. The four groups are neutral fats, phospholipids, derived lipids and sterols. a. Neutral fats or true fats:These are esters of one molecule of glycerol with three

96

8 Lipids

molecules of fatty acids. These are chemically known as triglycerides or triacylglycerols. True fats are major compounds of plant or animal fats— constituting 98–99% of total lipids. b. Phospholipids: These are compound lipids comprising of esters of fatty acids, phosphoric acid and generally a nitrogenous base, viz. lecithin, cephalins, etc. c. Derived lipids: These are free fatty acids and hydrolysates of triacylglycerols, viz. mono and diaceylglycerols. d. Sterols: These are compounds with ring structure and these are not fats or fatty acids. The important members of this group are cholesterol in animals and ergosterols in plants. Both are precursors of vitamin group. 4. Old system of classification (by W.R. Bloor in 1925–26): The lipids were classified on the basis of chemical nature. These were divided into groups and subgroups as follows: a. Simple lipids: These are esters of fatty acids with different kinds of alcohols. These include fats (including oils) and waxes. Fats: These are glycerol esters of fatty acids. These are nutrients providers. Waxes: These are esters of fatty acids with alcohol other than the glycerol. These do not provide any nutrient. b. Compound lipids: These are esters of fatty acids containing the molecule of some other compound in addition to fatty acids and alcohol. The additional molecule may be phosphoric acid, sugar or amino group. Phospholipids: The additional molecule in fats is phosphoric acid and a nitrogenous moiety, viz. lecithins and cephalins. Glycolipids: The additional groups lipid molecule is an amino group. Sulpholipids: The additional molecule is a sulphur compound. c. Derived lipids: These are mostly hydrolysis products of simple and other lipids. Fatty acids: A fatty acid a carbolic acid with long aliphatic chain, which is either saturated or unsaturated. Sterols: These are non-fat lipids extracted with fats in organic solvents. Hydrolysis Products of Saponifiable Lipids Fatty acids are common constituents of all the saponifiable lipids. The other variable components differentiate these lipids into different types of other lipids (Table 8.1). 1. Simple lipids: These are esters of fatty acids and alcohol and include true fats and waxes. The two classes differ due to different alcohol moiety. Fats Earlier fats and oils were used for the triacylglycerols extracted from the animals and plants respectively. Later on two groups were merged as fat or true fat. All the fats are triglycerides or triacylglycerols. In true fats, the alcohol moiety is always glycerol.

8.2 Classification of Lipids

97

Table 8.1 Saponifiable lipids Sl. No. 1. 2.

3. 4.

Saponifiable lipids Fats (including oils) Phospholipids (a) Phosphoglycerides (b) Sphingolipids Glycolipids Waxes

Hydrolysis products Fatty acids + glycerol Fatty acids+glycerol+phosphoric acid + a polar alcohol group Fatty acids + sphingosine + Phosphoric acid + a polar alcohol group Fatty acids + sphingosine or glycerol + a monosaccharides Fatty acids + long chain alcohol

Composition of Fats Fats are triacylglycerols also called triglycerides. Glycerol moiety is common in all the fat molecules. The composition of fats depends on the constituent of fatty acids in the molecule. Due to development of efficient techniques of fats and lipids analysis now it has become possible to determine fatty acids composition of fats obtained from different sources. The fats extracted from vegetables and aquatic animals (fishes) are highly unsaturated and normally called oil due to liquid state at room temperature (25
C). The liquid state is generally due to high proportion of oleic acid (acto-decanoic acid), linoleic (octadecadienoic) acid and linolenic (octadecatrienoic) acid in their molecules. On the other hand, fats of mammals and most of the avian species are commonly known as fat due to their solid state at room temperature. However, hardness of fats depends to some extent on the nature of fats in the diets. Ruminants animals are exception due to microbial alterations in the composition of dietary fats. The ratio of saturated fatty acids of high molecular weight like palmitic acid (hexadecanoic acid) and stearic acid (octadecanoic acid) is quite high in hard fats. Other statured fatty acids present in considerable amount in depot fats of animals are lauric (dodecanoic) and myristic (tetradecanoic) acids. The fats of mammalian species like butter, lard and tallow are solid at room temperature but fatty acids composition of these fats differs considerably due to dietary sources and metabolism. The effects of dietary lipids are more in simple stomached animals and birds than in the ruminants because microbial metabolism in rumen causes hydrogenation of dietary oils. The common fatty acids of plant and animal fats are oleic, palmitic and stearic acids. The vegetable oils contain very high percentage of unsaturated fatty acids which are more than 90% in mustard-rape seed oil which includes about 45% erucic acid (22:1) contents of some important saturated and unsaturated fatty acids in the fats of animals and plants are presented in table.

98

Fats Animal fats Butter (cow) Human milk Lard Tellow Spermaceti Vegetable oils (fats) Coconut oil Cotton seed oil Groundnut oil Linseed oil Maize oil Mustard/rape oil Olive oil Palm oil Safflower oil Sesame oil Sunflower oil

8 Lipids Saturated Palmitic

Stearic

Total

Unsaturated fatty acids Oleic Linoleic Linolenic

29 21 26 28 14.5

13 7 20 21 1.1

70 – 46 55 33

28 – 43 40 51

2 – 11 4 Traces

– – – – –

30 – 45 45 67

8 23 13 7 11 3 13

2 1 2 5 2 1 2

90 26 21 12 13 11 15

8 23 48 16 30 9 7

2 51 30 16 57 18 10

– – – 56 – 15 –

10 74 78 88 87 89 85

Total

Structure of Fats The main constituent of true fats or neutral fats are fatty acids and glycerol which is a trihydric alcohol and binds with three molecules of fatty acids. In the process is esterification all true fats or neutral fats of plant and animal origin are triacylglycerols also called triglycerides. The chemical binding of three molecules of fatty acids with 1 molecule of glycerol yields one molecule of triacylglycerol (true fat) and 3 molecules of water are released. The carbon atoms of glycerol molecule are numbered as 1, 2 and 3 in descending order. These positions of carbon are not identical and determined by specific enzymes in stereochemistry and may cause preferential reaction at any one of the three positions of carbon in the glycerol molecule. A common example of preferential reaction is phosphorylation, which always occurs at carbon atom 3 and not at the carbon position 1. The size and chemical nature of “R” may be same or different in a molecule of fat. Different fatty acids in a molecule are designated R1, R2 and R3 in a heterotriacylglycerol molecule. This is also called mixed triacylglycerol. Natural fats are mostly heterotriacylglycerols but occurrence of homotriacylglycerols or simple fat cannot be ruled out. A molecule of triacylglycerol produced from the reaction of one molecule of glycerol with three molecules of stearic acid is tristearin, but another product with three different fatty acid molecules is a heterotriacylglycerol like most present in the natural fats of plants and animals. These are generally a mixture of oleic, palmitic and stearic acids with first one unsaturated and last two saturated fatty acids. This product (fat) may be named as palmito-stereo-oleorin. In mixed triacylglycerol coconut fat (oil) is dominated by

8.3 Properties of Simple (Neutral) Fats

99

lauric acid ester (about 48%), whereas lard is generally dominated by oleic acid ester (about 54%). The R1, R2 and R3 in structure may be palmitic, stearic and oleic group, respectively. This heterotriacylglycerol molecule is known as 1-palmitoyl-20-oleoyl 3-stereoylglycerol or palmito-oleo stearin shows the number, position and type of fatty acids on the glycerol molecule.

8.3

Properties of Simple (Neutral) Fats

The natural fats of plants and animal origin are mostly heterotriacylglycerols. Normally fats of plant origin contain higher proportion of unsaturated fatty acids like oleic and linoleic acids. Contrary to this fats of animal origin are dominated by palmitic and stearic acids. The fatty acids composition of fat samples from different parts of same specimen frequently differs and variation is more in the samples of animals species. 1. Physical form or appearance: All fats are liquid at room temperature (20
C or 25
C) in different countries are commonly called oils. Natural fats of majority of plants are oils in appearance. Majority of fats of animals species are solid or semisolid at room temperature. Fats of most of the fishes are liquid at room temperature. 2. Solubility: Fats are insoluble in water but soluble in organic solvents like benzene, ether, hexane, acetone, chloroform, etc. 3. Melting point: It is highly variable among the fats due to significant difference in the ratios of saturated and unsaturated fatty acids in the fat molecules. The values are higher for the solid form of fats at room temperature and lower in semi-solid and liquid forms in descending order. The molecular weight of constituent fatty acids in the fats also influences melting point and values are lower for the fatty acids of lower molecular weight (table). The value of melting point is always higher than the value of solidification of the fats. 4. Iodine number of iodine value: It is a measure of unsaturation of a fat. Treatment of fats with iodine solution results in the incorporation of two atoms of iodine at each double bond which shows the degree of unsaturation of fat. This is presented as numbers of grammes iodine combined with 100 g of fat. The iodine number is more than 100 for most of the vegetable oils and much less than 100 for most of the animal fats. 5. Saponification value or saponification number: The number of molecules of an alkali (NaOH) utilized for the saponification (esterification) of 100 g of fat is known as saponification value. The incorporation of alkali molecules depends on the number of fatty acids molecules, i.e. the length of the fatty acids chain. The incorporation of alkali is more in fat molecules of short chain fatty acids. Alkali reacts with only acid moiety terminals of the fatty acids in a fat molecule. More number of short chain fatty acids are present in 100 g fat. The saponification reaction divides a fat molecule into saponifiable and non-saponiafiable parts. The

100

8 Lipids

saponifiable fraction is fatty acids and the non-saponifiable fraction contains sterols. 6. Reichert–Meissl number: This is a measure of determining soluble volatile fatty acids (VFAs) in the fats. The percentage of soluble volatile fatty acids in fats is the Reichert–Meissl number. It is useful for the detection of adulteration in butter fat. 7. Hydrolysis of fats: Two methods of hydrolysis of fats are the (a) chemical method of saponification by boiling with an alkali (NaOH/KOH) for determining the length of constituent fatty acids. (b) Enzymatic hydrolysis in natural conditions caused by the enzymes known as lipases. This kind of hydrolysis of fats is known as lipolysis. Hydrolysis of fats in natural environment may differ due to specificity of reaction of different lipases for attacking specific positions in a fat molecule. In a triacylglycerol molecule the carbon atoms at positions 1 and 3 are more reactive and position 2 is least reactive. Enzymatic hydrolysis of fats in nature produces a mixture of mono-acylglycerols, diacylglycerols and free fatty acids. The concentration of fatty acids of lower molecular weights like butyric and caproic acids in the hydrolysates of fats imparts unpleasant odour and repulsive taste. Fats are naturally hydrolyzed in bad storage conditions by the enzymes of bacteria and fungi. The reaction is known as rancidity and accelerated by presence of moisture and rise of temperature. 8. Oxidation of fats: Incorporation of oxygen at the double bond in unsaturated moiety in the fats is the process of oxidation. Both induced and anti-oxidation occur in the fats. Auto-oxidation is the spontaneous chemical reactions of molecular oxygen (O2) with fats or fat component of foods and compounded feeds producing irreversible chemical compounds is known as auto-oxidation or rancidity. All fats and fat soluble substances like vitamins and pigments are highly susceptible for degradation by auto-oxidation and oxidation as well. Auto-oxidation is a series of chemical reactions in the presence of air, moisture, light, heat, metals and microorganisms (enzymes of microbial origin). The entire process of oxidation is carried through three successive reactions and after some time simultaneous reactions. The three steps of auto-oxidation of fats are (i) initiation, (2) acceleration and termination as shown in Fig. 8.1. Different kinds of intermediate products of oxidation like peroxides and hydrogen peroxide are tasteless and odourless. But, various stable products like hydrocarbons, alcohols, ketones, aldehydes and short chain organic acids are produced from the dissociation of hydrogen peroxides. Most of these end products will emit characteristics offensive odour and their taste is abnoxious. Presence of aldehydes and ketones even in traces is quite potent to spoil the flavour of entire food. Presence of such foods may cause nausea and vomiting sensation in humans. The end products of auto-oxidation of fats and fat soluble substances are highly hydrophilic due to presence of a residual carbonyl molecule. These are compounds of small molecular weight due to which their passage in circulation is very easy. Entrance of such reactive molecules in the blood circulation is highly undesirable as these molecules cause oxidation in body tissues.

8.3 Properties of Simple (Neutral) Fats Table 8.2 Effect of heavy metal ions on oxidative stability of soyabean oil

Metal ion Fe+++ Mn++

101 Concentration (ppm) 3.0 3.0

Peroxide value 293.0 85.4

Factors causing and promoting auto-oxidation: Various factors responsible for auto-oxidation of fats and fatty foods/feeds are air (oxygen), moisture, light, metallic ions, temperature, enzymes (bacteria, fungi and moulds) and type of fats. 1. Air (oxygen): This is the main factor of oxidation and promoting the rate of oxidation in fats and fatty foods. The process can be drastically reduced by vacuum creation during packaging for storage and transportation. Even minute quantity of only 0.016% oxygen by weight of fat generation of peroxide value is 20 mEq of oxygen. 2. Moisture: It is responsible for the hydrolysis of fats producing fatty acids. It is also reaction medium and needed for multiplication of microorganisms. 3. Metallic ions: These are catalysts for the initiation of auto-oxidation reactions and production of free radicals. Trace elements such as copper, manganese, iron and zinc are highly active catalysts. An example for the effects of different heavy metal ions on oxidative stability of some unsaturated fatty acids rich soyabean oil on the basis of peroxide value is shown in Table 8.2. Blood meal is a rich source of iron due to which use of blood meal or blood meal mixed with meat meal may accelerate oxidation of fat causing rancidity of feeds with these ingredients. 4. Temperature or Heat: Auto-oxidation is a highly reactive process. It is highly sensitive for fluctuations in storage temperature of fats and fat containing foods and feeds. The process is further accelerated by increase in duration of high moist heat, low temperature may also produce oxidation and it has been observed in frozen meat stored for longer duration of several weeks and months. 5. Light: Energy provided by light accelerates the oxidation reaction of fats and fat containing feeds/foods. Among the light rays, the ultraviolet rays are more reactive. Oxidation reaction in light is much faster than the other factors involved in oxidation. 6. Type of fat: Oxidation rate is much higher in fats and foods containing higher ratio of unsaturated fatty acids. Saturation of fatty acids increases stability against oxidation (Table 8.3). 7. Enzymes/microbial activities: oil seeds and oil seed cakes/meals contain several enzymes to promote oxidation when released free on crushing the seeds rupturing cells. These enzymes are herbal lipases, lipoxygenases. In favourable conditions, herbal lipases hydrolyse triacylglycerols into free fatty acids.

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Table 8.3 Oxidation rate of fatty acids Fatty acids Stearic acid (18:0) Oleic acid (18:1) Linoleic acid (18:2) Linolenic acid (18:3)

8.4

Allyl group (double bonds) 0 1 2 3

Initiation period (h) – 52.00 19.00 1.34

Oxidation rate at 25
C 1 100 1200 2500

Controlled Use of Hydrolysis and Oxidation of Milk (Coagulan/Curd) for Cheese Production

Oxidation and hydrolysis by the use of enzymes of specific microorganisms have application in cheese manufacturing. Special strains of different microorganisms are used for the development of characteristic aroma and colour in cheese. Hydrogenation occurs only in unsaturated fatty acids in which hydrogen atoms are incorporated at double bond in the molecule of fatty acids. This process causes saturation of unsaturated fatty acids and called hydrogenation. By the process of hydrogenation more reactive unsaturated fatty acids are converted to much less reactive saturated fatty acids of neutral fats, viz. addition of hydrogen molecule (H2) at the double bond of oleic acid produces stearic acid as follows: CH3(CH2)7 CH=CH (CH2)7 COOH+2H Oleic acid

Hydrogen

CH3(CH2)16.COOH Stearic acid

Hydrogenation of fats has important industrial use by converting liquid fats to considerably hard fat of solid consistency at room temperature. This process is extensively used for the manufacture of margarine and hydrogenated vegetable fats. The process is catalysed by nickel at 15 kg/cm2 pressure. In natural conditions ruminants consume good amount of unsaturated fats from their herbaceous diets but their body fat is made up of greater proportion of saturated fatty acids that increase melting point. Fats eaten by the ruminants are first hydrolysed by the microbial enzymes and then bio-hydrogenated in the rumen to produce saturated fatty acids. Hardening of fats by hydrogenation has many advantages like easy packaging, convenient transportation, longer shelf life and almost neutral reaction due to removal of the double bond in molecules.

8.7 Waxes

8.5

103

Antioxidants

The chemical substances preventing the oxidation of lipids are known as antioxidants. These are natural as well as synthetic. Duration of prevention of oxidation of fats by natural antioxidants is quite variable. It depends on the resistance ability of fats and potential of the antioxidants. Tocopherols (vitamin E) are one of the most potent and effective antioxidant naturally occurring in the fats. The other antioxidants are phenols, quinones, gallic acid and gallates. The common gallates are propyl-, octyl- and dodecayl gallate. Another group includes butylated hydroxyamisole, butylated hydroxytoluene and ethoxyquinone. The amount of antioxidants in edible fats and fatty foods/feeds is regulated by the food safety laws applicable in different countries like PFA in India. Some synthetic antioxidants like derivatives of ascorbic acid (vitamin C) and alpha, beta and delta tocopherols may be used in large amounts and these are free from control in many countries.

8.6

Animal Fats

In the early years of the twentieth century, animal’s body fats were distinguished into two groups of (1) constant element and (2) variable element. It was believed that during deficiency caused by inadequate dietary supply, variable element is immediately drawn to supply the energy requirements for body functions. This was also believed that constant element is not mobilized and remains in position to maintain the essential features of body (tissues and cells). Later on it was shown that all body fats remain in dynamic state even if the supply is adequate or higher. However, it was observed that constant element represents the fat that are essential for the normal functions as constituent of cells. These are mainly phospholipids and sterols. On the other hand, variable element represents the bulk of body fat deposited as energy reserves in depot fats. The depot fats are largely triacylglycerols of palmitic, oleic and stearic acids with very little amount of other lipids. The fatty acid composition of body fat differs among species of animals. Softer body fat of cold blooded animals is due to higher proportion of unsaturated fatty acids in comparison to warm blooded animals particularly the ruminants. Body fats of ruminants is harder than the body fat of ominivorous and carnivorous animals. Nature or composition of body fat is also influenced by the type of dietary fat, protection of dietary fats from ruminal actions and site of deposition in the body.

8.7

Waxes

The waxes are indigestible simple or neutral fat produced from the esterification of fatty acids with monohydric or dihydric alcohols of higher molecular weight. These are hard at room temperature due to very high melting point. Rarely these are fatty acids of lower molecular weight in waxes. Most common alcohols used for the

104

8 Lipids C31H31COOH + C31H63OH Palmitic acid

Myrocyl

C15H31COOH + C16H33OH Palmitic acid

Cetyl

C15H31COOC31H63 + H2O Myricyl palmitate C16H31COOC16H33 + H2O Cetyl palmitate

Fig. 8.2 Wax formation

synthesis of waxes are cetyl alcohol (C16H32OH), carnaubyl alcohol (C24H49OH) and myricyl alcohol (C31H63OH). Natural waxes are mostly mixture of several esters of higher fatty acids. Bee wax is formed of minimum five different esters, the main is myricyl palmitate (Fig. 8.2). Natural waxes are widely synthesized by plants and animals for protective functions.

8.8

Properties of Waxes

1. 2. 3. 4. 5. 6.

These are hydrophobic, insoluble in water. Indigestible in animal body. These are rich in energy but not useful for animals as dietary energy source. These are highly inflammable. Waxes are grazy in appearance due to which extensively used in polish. Prevents dehydration of herbages and form thick protective layer on cladodes, phylloclades and leaves of arid plants. This drastically reduces loss of moisture from plants by transpiration. 7. Waxes provide water proofing of body of aquatic and semi-aquatic animals. 8. Waxes provide protection to wool and that is linolin. 9. Waxes are indigestible due to high melting points and non-saponification property resulting in non-availability of fatty acids for digestion and metabolism.

8.9

Some Natural Waxes

1. Lanolin provides protection to wool. 2. Suberin is present on the surface of underground parts of herbages and also on healed wounds. 3. Spermaceti is a wax obtained from whales and used in cosmetics particularly for making lipsticks.

8.10

8.10

Compound Lipids

105

Compound Lipids

The lipids containing a prosthetic group other than ester in the molecules are known as compound lipids. The prosthetic groups are phosphoric acid, galactose and amino acids. The last one has been included in proteins. 1. Phospholipids: Compound lipids containing phosphorous in their molecules are known as phospholipids. These are components of every living cell, whether animal or plant cells. The content is quite large in nervous tissue, heart and kidneys. As a component of lipoproteins complexes of cell membranes, the phospholipids play a vital role in maintenance of cell structure and functions. The myelin sheath of nerve axon is made up of more than half of the lipids in mammals. Eggs and soyabeans are the rich sources of phopholipids. Phospholipids are one of the essential group of lipids which are conserve even during extreme starvation when almost all carbohydrates, most of the simple fats and proteins are utilized for survival. The phospholipids may be classified into (a) phosphoglycerides comprising of lecithins, cephalins and plasmologens, (b) phosphoinositides and (c) phosphosphingosides or sphingomyelins. a. Phosphoglycerides or phosphatides: These are made up from esterification of two alcohol groups of glycerol with fatty acids and one with phosphoric acid. The phosphorous can be esterified with any one of the alcohols like choline, serine, inositol, glycerol and ethanolamine. Main fatty acids of phosphoglycerides are 16 carbon saturated, 18 carbon saturated and monoenoic acids but fatty acids of 14 to 24 carbon atoms may also be present. The common phosphoglycerides in plants and animals are (a) the lecithins and (b) cephalins. A third phosphoglyceride (c) plasmogen contains enol form of a long chain aldehyde replacing one of the fatty acids of lecithins or cephalins and joined by ether linkage. Lecithins: These are white waxy materials soluble in organic solvents like alcohol and ether, etc. A molecule of lecithin contains phosphoric acid ester of a nitrogenous base choline due to which lecithins are chemically known as phosphatidylcholines. The hydrolysis products of lecithins are free carboxylic acid, choline and glycerophosphoric acid. The fatty acids at R1 position are generally palmitic or stearic acid; and R2 unsaturated oleic, linoleic or linolenic acid residues. b. Cephalins: The cephalins contain ethanolamine base in place of choline and called phosphatidyl-ethanolamine. The fatty acids are the same present in the lecithins and also occupy the same position in the molecule.

106

8 Lipids

c. Plasmogens or plasmalogens or ether phospholipids: These are also esters of glycerol but contain alkyl group in place of acyl group at carbon atom 1 as in glycosides. A vinyl ether group is present in plasmogens. These are mainly found in cardiac tissue but functions are not yet known.

8.11

Properties of Phosphoglycerides

1. These are not soluble in water but on placing in water these swell and apparently appear solubilized due to formation of micelles. 2. These are soluble in organic solvents. 3. Naturally occurring enzymes (phospholipases) are capable of hydrolysing phosphoglycerides cleaning certain specialized bonds of molecules releasing fatty acids, phosphate ester, glycerol and nitrogenous base. 4. The two phosphoglycerides join in the same molecule with both phosphate ester group and fatty acid chains are hydrophilic and hydrophobic, respectively. Due to this reason these molecules became surface active (surfactants) and may work as emulsifying agent in the duodenum of alimentary canal. These are also present in biological membranes and play a very important role of lipids transportation through the biological membranes. a. Phosphoinositides: This contains a vitamin inositol in its molecule. The hydrolysis products are fatty acids, phosphoric acid, glycerol and inositol. The activity of phosphoinositides is catalysed by phospholipase C. The functions of these lipids are not yet clear. b. Phosphosphingosides or splingomyelins: There are members of sphingolipids and contain sphingosine in place of glycerol. In the molecules of sphingomyelins the terminal hydroxyl group is bonded to phosphoric acid molecule and not with a sugar molecule. The phosphoric acid in these molecules combines with choline or ethanolamine to form esters. The sphingomyelin molecules also contain amino group linked to carboxyl group of a long chain fatty acids by peptide bond (Fig. 8.3). The sphingomyelins are also surface active and constituents of cell membranes, specially of nervous tissue cells. These are components of myelin sheath of nerve fibres and provide protection to nerves. These are hardly found in energy producing cells. Greater proportion of sphingomyelins is found in brain and nervous tissue.

Fig. 8.3 A sphingomyelin molecule

8.12

Derived Lipids or Non-saponifiable Lipids

107

2. Glycolipids: These are compound lipids containing a sugar moiety in the molecule in place of phosphate group. The sugar molecule may be glucose or galactose. Cerebroside is the simple example of glycolipids. The number of sugar molecules may be more, e.g. 7 molecules are present in gangliosides. High ratio of glycolipids are found in the brain and nervous tissue. An example of galactolipid. The lipids of green vegetation are rich sources of galactolipids due to which diets of grazing animals and those fed larger proportion of green fodder provide up to 60% galactolipids. The herbal galactolipids are mostly monogalactosyl along with a small fraction of digalactosyl. The fatty acids of galactolipids of herbages are more than 95% linolenic acid and traces (2–3%) of linoleic acid and other fatty acids. These are hydrolysed by galactoses of ruminal microorganisms into galactose, fatty acids, glycerol and nitrogenous group. The galactolipids are constituents of brain and nervous tissue of animals.

8.12

Derived Lipids or Non-saponifiable Lipids

The organic compounds of plants and animals associated with lipids but they are not fats. These are extracted with fats and called derived lipids. 1. Steroids: These are cyclic compounds having a common basic unit of phenanthrene (Fig. 8.4) nucleus combined with a cyclopentane ring structure. In this unit carbon atom 17 in the pentagonal cyclopentene ring is most reactive and the side chain bonded with this carbon atom differentiates them in different steroids. The basic phenanthrene unit is made up of three hexagonal rings A, B and C and a cyclopentene ring D. The steroids contain one or more carboxy or carbonyl groups. Steroid Hormones Both male and female sex hormones are steroids containing basic phenanthrene nucleus unit linked with a cyclopentane ring. The female sex hormones are oestrogens and progesterone. Both the hormones are synthesized in ovaries but progesterone is more closely related with the androgens. The male hormone testosterone is synthesized in testis and then changed to androsterone which is detected in urine. The steroid hormones are synthesized in sex glands from cholesterol. 2. Sterols: These are lipid like substances possessing alcohol group at carbon atom 3. The side chain of sterol molecules contains 8–10 carbon atoms. There is no Fig. 8.4 Phenanthrene nucleus

108

8 Lipids

carboxyl (–COOH) or carboxyl (>C¼O) group in the molecule. One of the basis of source of origin the sterols are placed in the following three groups. a. Zoosterols are produced in animals, e.g. cholesterol. b. Phytosterols are produced in plants, e.g. ergosterol. c. Mycosterols produced by some fungi. Cholesterol: It is a constituent of all living cells of the animal body. It is not found in plant cells. Sites of cholesterol in a cell are the surface and intracellular membranes. The concentration of cholesterol is more in myelin sheath and may be about 17 percent of dry matter against only 0.12–0.26 g/dl in blood plasma and 0.06 and 0.17 g/dl in the bile. Plasma cholesterol is mostly present in esterified form. In cell membranes it occurs in free form. Cholesterol is also present in the bile and its name has also derived from the greek words “chole” means bile and “streos” means solid. These two words were merged to make cholesterol. Other sites of cholesterol are the living and egg yolk. Structure of cholesterol is shown in Fig. 8.5 below. The lipoproteins in plasma is made up of a core of triacylglycerols and cholesterol esters surrounded by a 20 of thick capsule of a complex mixture of unesterified cholesterol along with phosphatidylcholine and protein. These complexes are found as spherical bodies in the plasma. The surface area to volume ratio due to which smaller globules contain more lipids than the proteins. Lipids content in high density low protein (HDLP) fraction is about 55% against 90% in very low density protein (VLDP). The protein content in HDLP and VLDP is about 45 and 10%, respectively. The lipoproteins are placed in five groups on the basis of density (Table 8.4). The composition of lipoproteins and chylomicron is presented in Table 8.5. Fig. 8.5 Cholesterol

Table 8.4 Lipo-proteins Class Lipoproteins high density (HDLP) Low density lipoproteins Intermediate density lipoproteins Very low density lipoproteins (VLDL) Chylomicrons

Mass/density (g/ml) 1.063–1.210

Molecular weight (Daltons) 2–4  105

Diameter of globule 50–130

1.019–1.063 1.006–1.019

2  106 4.5  106

200–280 250

0.095–1.006

5  107

250–750

16% moisture and stored aerobically. The possibility of manipulating gastric pH by adding of organic acid in the drinking water has also reported beneficial effect in animal. Use of lactic acid may also control or prevent diarrhoea associated with some bacterial infection by lowering the pH, which inhibits multiplication of enteropathogenic microorganisms (E. coli), chemicals other than acids, hydrogen diacetate may be used to exert similar influence on gastric pH. Other chemicals, for example,

13.2

Mode of Action of Feed Additives

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hydrocolloids added to the diet can affect the physical form of digesta and its rate of passage through the gastrointestinal tract. Various gums, such as agar, carrageenan and carob bean gum, sodium alginate and sodium carboxymethyl cellulose affect the adsorption of water and accelerate the rate of passage of digesta there by reduces the untoward pathogenic microbial fermentation. However, non-acidified diets are more desirable. The magnitude of response is likely related to nature of diet with greatest benefit with cereal grain supplemented with plant proteins. Vegetable protein diets are more difficult for the weaner pigs to digest than are diets having milk protein as the supplemental amino acid source and the vegetable protein diet responded more to acidification compound with casein. The acid response on improved nitrogen and dry matter digestibility may decline with maturation of the gastrointestinal tract. Malic acid is used in animals on high grain finishing diets which may be beneficial in promoting a higher rumen pH during periods of peak acid production without detrimental effects on rumen microbial efficiency or starch, fibre and protein digestion (Montano et al. 1999). Sodium fumarate may be useful as it diverts some H2 from CH4 production and also able to stimulate proliferation of cellulolytic bacteria and digestion of fibre. Hydrochloric acid, sulphuric acid, phosphoric acid and fumaric acid are also used for acidification. In addition to acidification, the former two acids changed the dietary electrolyte balance and phosphoric acid provides inorganic phosphorous.

13.2.7 Drugs Anthelmintics, coccidiostats and deworming drugs are routinely used in the diets of animals to prevent sudden economical loss due to coccidiosis in poultry and also to improve intake and utilization of feed maintaining a healthy intestinal environment for better nutrient absorption and assimilation.

13.2.8 Hormones Hormonal preparation are used in animal feeding in order to bring about durable changes in the nature and rate of metabolism for efficient productivity and can be grouped under functional categories, viz. anabolic and catabolic hormones. The hormones improve the important regulatory activities like growth, differentiation, reproduction, maintenance of the internal environment and adaptation to changes in the external environment. The anabolics are growth hormones and thyroxine, which are being used for productivity, e.g. bovine somatotropin (bST) for increase milk production, iodinated casein to improve egg production, eggshell quality. The catabolics, oestrogen and glucocorticoids are used to increase muscle and bone formation at the expense of fat deposition thereby improving the carcass finish. The commercial preparation are BST, iodinated casein, desiccated thyroid glands, diethyl stilbosterol, estradiol benzoate, dienestrol diacetate, testosterone, propionate, thiouracil, etc. which act as agonists and are chemical messenger that activate

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adrenergic receptor and stimulate the breakdown of fat in the cell and increase the rate of oxidation of free fatty acids and thus more of energy is obtained and made available to the body for protein synthesis. These are used to stimulate production of muscle while limiting the synthesis and deposition of subcutaneous and internal fat.

13.2.9 Enzymes Enzyme supplements or pretreatment of feeds with enzymes are of limited use in ruminants but their applications may be more useful in pre-ruminant calves and especially in non-ruminants. In poultry diets supplemental enzyme could be used for increasing bioavailability of polysaccharide and proteins increasing the nutritive value of poor quality feeds and hydrolysing in the digestive systems which is not fully developed (Lawrence 1986; Pallof and Rumbach 1977; Kenme et al. 1999). Enzymes can increase the availability of metabolizable energy (AMS) by (1) Breaking down non-starch polysaccharides (NSP) not usually degraded by the animals, (2) Increasing the amount of nutrients available for digestion by releasing b-linked hexoses and pentoses from the cellulose and hemicelluloses complexes, (3) Providing a wider choice of raw materials by upgrading the value of feedstuffs and (4) Supplementing enzymes that are being inhibited by enzyme-inhibiting factors inherent in certain feeds stuffs (trypsin inhibitor, etc.). The commercial enzyme preparations have different mode of action and the development of improved products depends on thermal stability, pH profile, substrate specificity and proteolytic stability in the digestive tract. The enzymes responsible are b-glucanase and pentosanase (xylanase) to cleave b-linkages in non-starch polysaccharides (pensosans, arabinoxylans, b-glucans, etc.), phytase to cleave the ester linkage in phytin or phytic acid, cellulases and hemicellulases to cleave b-linked glucose units in fibre complex (cellulose hemicelluloses and lignin). Other enzymes used are trypsin as supplement for antitryptic activity in soybean meal, tannase in high tannin diets, amylase in starchy diets, etc. Hristov et al. (1998) supplemented polysaccharide degrading enzymes containing celluloses, amylases, xylanases, etc. through the abamasum, but found non-significant changes as there was loss of enzymatic activity at low pH and due to pepsin proteolysis. It is reported that increased cell wall degrading bacteria in the rumen by feeding the enzyme extracts of Aspergillus niger and Saccharomyces cerevisiae.

13.2.10 Antifungal Agents Sodium propionate, sodium benzoate, quaternary ammonium compounds and certain antifungal antibiotics like nystatin are sometimes used as feed additives to retard fungal growth in storage feeds. Hydrated sodium calcium alumino-silicate, a zeolite from natural one combats aflatoxin problem through adsorption and then passes

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through gastrointestinal tract nullifying the toxin affecting animal health. However, the more desirable method of controlling fungal infestation is by maintaining proper temperature and proper humidity in godowns so that the moisture level in feed should remain at