The International Sheep and Wool Handbook [Second Edition, Second edition] 1904761860, 9781904761860

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World sheep population and production i

INTERNATIONAL SHEEP AND WOOL HANDBOOK

EDITED BY DJ COTTLE

ii D. Cottle

Nottingham University Press Manor Farm, Main Street, Thrumpton Nottingham, NG11 0AX, United Kingdom NOTTINGHAM First published 2010 © DJ Cottle All rights reserved. No part of this publication may be reproduced in any material form (including photocopying or storing in any medium by electronic means and whether or not transiently or incidentally to some other use of this publication) without the written permission of the copyright holder except in accordance with the provisions of the Copyright, Designs and Patents Act 1988. Applications for the copyright holder’s written permission to reproduce any part of this publication should be addressed to the publishers. British Library Cataloguing in Publication Data International Sheep and Wool Handbook: Ed. DJ Cottle ISBN 978-1-904761-86-0

Disclaimer Every reasonable effort has been made to ensure that the material in this book is true, correct, complete and appropriate at the time of writing. Nevertheless the publishers, the editors and the authors do not accept responsibility for any omission or error, or for any injury, damage, loss or inancial consequences arising from the use of the book.

Typeset by Nottingham University Press, Nottingham Printed and bound by Gutenberg Press Ltd, Malta

World sheep population and production iii

FOREWORD

It is with great pleasure that the International Wool Textile Organisation (IWTO), the international body representing the interests of the world’s wool-textile trade and industry, salutes David Cottle on this comprehensive coverage and most informative handbook on the sheep and wool industry. The handbook will serve both as a reference work to students and to those with a general interest in the sheep and wool industry. IWTO membership covers woolgrowers, traders, primary processors, spinners, weavers, garment makers and retailers of wool and allied ibres in its member-countries, as well as all kinds of organizations related to wool products and the Wool Industry in general. Thus in this context the book covers the interests of all our members in all parts of the World, from the production of wool at its source through to the inished garment sold in the retail store. We are indebted to Prof. David Cottle for producing such a comprehensive and interesting study of the sheep and wool industry. This is something which we have not had in the past and thank him and his colleagues most sincerely for the time and effort that they have put into researching and documenting every facet of our industry. As the drive towards naturally sustainable and ecologically friendly ibres becomes more important, books of this nature will become all the more relevant in showing the beneits of wool.

Günther Beier IWTO President

iv D. Cottle

World sheep population and production v

CONTENTS FOREWORD PREFACE

V

vii

MAJOR WORLD SHEEP AND WOOL INDUSTRIES

12 13

1

WORLD SHEEP AND WOOL PRODUCTION

WEANER MANAGEMENT

277

AJD Campbell

1

DIGESTION AND METABOLISM

295

DJ Cottle

DJ Cottle

14 2

AUSTRALIAN SHEEP AND WOOL INDUSTRIES 49

FEEDING

331

S Jolly and DJ Cottle

DJ Cottle

15 3

NEW ZEALAND SHEEP AND WOOL INDUSTRIES SOUTH AMERICAN SHEEP AND WOOL INDUSTRIES

16

SOUTH AFRICAN SHEEP AND WOOL INDUSTRIES

85

17 95

18

CHINESE SHEEP AND WOOL INDUSTRIES 113

19 20

21

PREGNANCY, LAMBING AND SURVIVAL LACTATION AND LAMB GROWTH KG Geenty

FARM STRUCTURES

PRODUCTION SYSTEMS

189

22

445 471

489

EXTENSIVE GRAZING SYSTEMS

507

RB Hacker

223

23

COARSE WOOL PRODUCTION

533

RMW Sumner

P Celi and R Bush

11

SHEEP HEALTH

165

SP de Graaf

10

SUSTAINABLE LIVESTOCK PRODUCTION

PD Hanrahan

J Greeff, BP Kinghorn and D Brown

REPRODUCTION

425

B Besier, C Jacobson, R Woodgate and K Bell

BIOLOGICAL PRINCIPLES

9

PASTURE MANAGEMENT

B Gardiner and N Reid

EUROPEAN SHEEP AND WOOL INDUSTRIES 153

BREEDING AND SELECTION

407

JE Pratley and JM Virgona

C Popescu

8

SHEEP MANAGEMENT KJ Bell

JW Longworth, CG Brown and SA Waldron

7

395

MANAGEMENT

SWP Cloete and JJ Olivier

6

MEAT PRODUCTION G Geesink and H Zerby

I Abella, RC Cardellino, J Mueller, RA Cardellino, D Benítez and R Lira

5

373

73

AR Bray and E Gonzalez-Macuer

4

WOOL GROWTH AND PRODUCTION GE Rogers and AC Schlink

259

24

INTENSIVE PRODUCTION SYSTEMS G Gaunt, S Jolly and G Duddy

565

vi D. Cottle

PREPARATION, PROCESSING AND MARKETING 25

WOOL PREPARATION, TESTING AND MARKETING

A B 581 C

DJ Cottle

26

WOOL PROCESSING THE FUTURE OF WOOL AS AN APPAREL FIBRE

NUTRIENT COMPOSITION OF FEEDS AUSTRALIAN SHEEP ENTERPRISE GROSS MARGINS AUSTRALIAN WOOL AND SHEEP MEAT PRICES WORLD WOOL TYPES

711 717 721 725

619

D

647

GLOSSARY OF SHEEP AND WOOL TERMS

733

661

INDEX

751

EJ Wood

27

APPENDICES

P Swan

28

SKINS D Scobie

29

MARKETING OF SHEEP AND SHEEP MEAT 677 BM McLeod, AK White and WJ O’Halloran

30

PROCESSING OF SHEEP AND SHEEP MEATS 691 DL Hopkins

World sheep population and production vii

PREFACE This book is an expanded, updated version of the Australian Sheep and Wool Handbook published in 1991. The 1991 text was widely regarded as the deinitive sheep and wool textbook and has been used as the reference text for sheep and wool subjects in many Universities since then. In the 1990s there were few sheep and wool textbooks available compared to the situation in 2010. Many requests were received over the last 19 years to produce a new edition. The amount of time required to produce a new, substantive book caused some trepidation but a rare window of opportunity to carry out the task opened up in 2008-2009. One massive change that has affected both the sheep and wool industry and the publishing industry is the advent of the internet with its search engines, word processing software and the use of email. This has made multiauthored book writing easier and quicker on the one hand but with the increased problem of possible information overload. Much of the value of this book for readers is the distillation of the mountain of information available in the modern digital, electronic era by the chapter authors sifting through the various sources of information and capturing it in one place. Key websites for further information have been listed at the end of many chapters.

The book has been made more international in scope compared to the earlier 1991 text. There is the collection of new chapters on the sheep and wool industries in the major sheep regions of the world which is unique to this book. There is also a wider range of references to global examples in the various chapters. There are new chapters on meat processing and sustainable production and expansion of some chapters, e.g. sheep meat and wool processing. The 1991 book was written at the time of the wool reserve price scheme collapsing in Australia. There has been much change in the meat and wool industries but some would argue not enough change. All authors were asked to crystal ball gaze about likely future developments. Perhaps this was a recipe for being proven incorrect in future but it was an interesting exercise. The Meat and Wool Boards were merged in New Zealand and in 2009 the NZ growers voted to reduce the wool levy to zero. Australian producers voted to maintain a 2% wool levy in WoolPoll 2009 but there have been calls to merge the wool (AWI) and meat (MLA) organizations. What changes will the next 20 years bring to the world sheep and wool industries?

DJ Cottle

vii

World sheep and wool production 1

WORLD SHEEP AND WOOL PRODUCTION

1

DJ Cottle Woolshed, University of New England E-mail: [email protected]

Early history The word sheep is derived from the Old English or AngloSaxon (around 450 to 1150 AD) term scap, which is akin to the Old High German (around 500 to 1050) scªf and probably originated from Proto-Germanic or Gothic terms (around 300-700). Before 1200 AD, English spelling preferred scheap, and the shift to the currently used spelling did not occur until about 1280. The word ram derives from the Old English rom and subsequently ramm (Barnhart, 1995). The word mutton is derived from the Old French (around 1000-1300) moton, which was the word for sheep used by the Anglo-Norman rulers of much of the British Isles in the Middle Ages (400 to 1500 AD). This became the name for sheep meat in English, while the Old English word scap was kept for the live animal (Oxford English Dictionary, 1933). Throughout modern history, mutton has referred to the meat of mature sheep while lamb is used for the meat of immature sheep less than one year old (see Chapter16). In the Neolithic period (starting around 10000 BC) a number of livestock species (e.g. goats, sheep, pigs and cattle) were domesticated in the Middle East and Asia, as farming spread during this period. Sheep were irst domesticated between 11000-9000 BC (Simmons and Ekarius, 2001). Initially, sheep were kept solely for meat, milk and skins, however some of the earliest human civilizations used felted or woven wool for clothes and fabrics. Archaeological evidence from statues found at sites in Iran suggests that selection for woolly sheep may have begun around 6000 BC (Ensminger and Parker, 1986; Weaver, 2005) but the earliest woven wool garments have only been dated at 4000-3000 BC (Smith et al., 1997). The oldest known European woollen textile, found in a Danish bog, has been dated at ~1500 BC. By the Bronze Age (2300-600 BC in Europe), sheep with all the major features of modern breeds were widespread throughout Western Asia (Ensminger and Parker, 1986). Primitive sheep could not be shorn and their wool was plucked out by hand in a process called “rooing”. Fleeces were also collected from the ield after shedding. This trait survives today in more primitive breeds such as the Soay and Wiltshire Horn. Soay, along with other Northern European breeds with short tails, shedding leeces, small size and horns, are closely related to ancient, wild sheep. Originally, weaving and spinning wool was done at home with Babylonians, Sumerians and Persians all raising locks

for their leece and as a medium of exchange. Some large locks were kept and subjects of the king of Israel were taxed according to the number of rams they owned (Ensminger and Parker, 1986). However, linen from lax, was the irst fabric to be fashioned into clothing. Prior to the invention of shears during the later Iron Age, wool was also plucked by bronze combs. In Roman times clothes were made from wool, linen and leather. Pliny the Elder recorded in his Naturalis Historia (77 AD) that the reputation for producing the inest wool was enjoyed by the town of Taranto in southern Italy (Isager, 1991).

Figure 1.1. An early picture of woollen cloth from the Tacuinum Sanitatis casanatensis, a fourteen-century handbook on good living, based on the Taqwin al-sihha, an eleventh-century Arab medical treatise. Source: Wickersheimer (1950). In the middle ages / medieval times (476-1453 AD) wool trading lourished. A series of six fairs in the Champagne and Brie regions of France, each lasting more than six weeks, were spaced throughout the year (at Lagny, then Bar-surAube, Provins and Troyes). At their peak, in the late 12th and 13th centuries, the Champagne fairs linked the woollen clothproducing cities of the French Netherlands (the low lands around the delta of the Rhine, Scheldt and Meuse rivers) with the dyeing and exporting centers of Genoa, Naples, Sicily, Cyprus, Majorca, Spain and Constantinople (Braudel, 1984; Munro, 2003). The wool trade was the economic lifeblood of these Low Countries and of Central Italy with most of the raw wool supplied by England and Spain. The English crown in 1275 imposed the irst export tax on wool called the ‘Great and Ancient Custom’ at 7s. 6d. per sack (Power, 1941). The tax was granted in Edward I’s

International Sheep and Wool Handbook

1

2 D. Cottle irst parliament, but it was negotiated by the king and wool merchants, including foreign merchants. The merchants received their quid pro quo in the shape of the resumption of open trade with Flanders (Ypres, Ghent and Bruges were amongst the most densely populated parts of Europe in the early 1200s). In 1273 export had been forbidden except by special paid licences. This was followed in 1274 by a still more stringent prohibition, more licences and an inquisition into smuggling. The importance of wool to the 14th century English economy is demonstrated by the fact that since then the Lord Chancellor of the House of Lords has sat on the Woolsack, a chair stuffed with wool brought from around the Commonwealth, with the even larger Judges’ Woolsack placed in front of it.

wild moulon (Meadows et al., 2007) or there may have been an unknown species or subspecies of wild sheep that contributed to the formation of domestic sheep (Hiendleder et al., 2007). The mouflon is red-brown with a dark back-stripe, light colored saddle patch and underparts and possesses an outer coat of coarse hair with an undercoat of short ine wool. The males are horned and the females are horned or polled. Five subspecies of Moulon were distinguished by Wilson and Reeder (2005). 1.

2. 3.

Foundation species Domestic sheep are ruminant mammals (see Chapter 13) kept as livestock. Like all ruminants, sheep are even-toed ungulates, also commonly called cloven-hoofed animals. The name sheep applies to many species however it usually refers to the species Ovis aries. Domesticated sheep are scientiically classiied as in the Kingdom: Animalia, Phylum: Chordata, Class: Mammalia, Order: Artiodactyla, Family: Bovidae, Subfamily: Caprinae, Genus: Ovis, Species: Ovis aries (Wilson and Reeder, 2005). Wild sheep (Ovis orientalis) can be partitioned into the Moulons (Ovis orientalis orientalis group) and Urials (Ovis orientalis vignei group). Domestic sheep are the most numerous species in their genus. They are most likely descended some 8,000-10,000 years ago from the wild moulon of Europe (O. musimon), of which the only existing members are on the islands of Sardinia and Corsica, and from O. orientalis, found in the dry and mountainous regions of south-western and central Asia (Zeuner, 1963). Ensminger and Parker (1986) proposed that the European moulon was an ancient breed of domestic sheep turned feral rather than an ancestor of modern domestic sheep. However, generally, the moulon is thought to be the main ancestor of all domestic sheep breeds including short-tailed sheep in northern Europe, such as the Romanov (Hiendleder et al., 2002; 2007). Urials occasionally interbreed with moulon in the Iranian part of their range (Ensminger and Parker, 1986). However, the Urial, Argali and snow sheep have a different number of chromosomes than other Ovis species, making a direct relationship unlikely and phylogenetic studies show no evidence of Urial ancestry (Hiendleder et al., 2002). The Argali, or mountain sheep (species Ovis ammon) is a globally endangered wild sheep, which roams the highlands of Central Asia, e.g. Altai and Himalaya foothills. It is the largest wild sheep, standing up to 1.2 m high and weighing up to 140 kg and is thought to be the ancestor of fat-rumped sheep. The snow sheep (Ovis nivicola) comes from mountainous areas in the northeast of Siberia. Studies comparing European and Asian breeds of sheep have shown signiicant genetic differences between them. This variation may be the result of multiple waves of capture from

4. 5.

European Moulon (Ovis orientalis musimon): about 7,000 years ago they appeared in Corsica and Sardinia for the irst time, Cyprian Moulon (Ovis orientalis ophion): Less than 1,200 of this subspecies survive, Armenian Moulon (Ovis orientalis orientalis): Caucasus, northwestern Iran and southern Anatolia. Sometimes also called gmelini, Esfahan Moulon (Ovis orientalis isphahanica): Zagros Mountains, Iran, Laristan Moulon (Ovis orientalis laristanica): Restricted to some desert reserves in southern Iran.

Figure 1.2. A Moulon. Source: J. Dennett (2006). The Urial is also known as the Steppe, Shapo or Arkhar. There are 7 recognized subspecies of Ovis vignei, although scientists are not agreed on the number of subspecies or their distribution. Steppe sheep are found on the borders of India to the Caspian Sea; they are the ancestors of long-tailed domestic sheep – e.g. Tsigai, Merino and fat- tailed sheep, such as the Karakul. CITES (2008) reported on endangered Urial population distributions and numbers as follows: 1.

2.

3.

4.

Afghan Urial or Turkmenian sheep (Ovis vignei cycloceros): southern Turkmenistan, eastern Iran, Afghanistan, northern Pakistan, Kashmir (>12,000 incl. blanfordi), Blanford Urial or Balochistan Urial (Ovis vignei blanfordi): Balochistan are often included in this subspecies, Transcaspian Urial (Ovis vignei arkal): Ustjurt-Plateau (Turkmenistan, Uzbekistan, northern Iran) and western Kazakhstan ( 0.5 (lambs) > 1.0 (sheep)

> 200 (depends on amount of wool)

Stun time 1 sec

Time to sticking Within 10 secs

Source: adapted from Hopkins et al. (1996).

Blood splash (ecchymosis) and speckle (petechial haemorrhages) can both be observed in stunned carcaseses. Blood splash is the escape of blood from blood vessels into muscle tissue and these haemorrhages appear as dark red spots (see Figure 30.5). The exact cause is not known, although it appears to arise from high blood pressure and possibly weak blood vessels, but is not common in lambs.

Figure 30.5. Lamb loin showing extensive blood splash evidenced as dark spots Source: D.L. Hopkins.

Figure 30.4. Application of a head stun to a sheep. Source: E.S. Toohey. Head to back stunners do reduce blood splash (Devine et al., 1982) because of a reduction in blood pressure, but this type of

Pre-slaughter stress may predispose lambs to blood splash by elevating blood pressure and it is known that ineffective stunning can also lead to higher blood pressure. Gregory (2005) suggested that with electrical stunning blood vessels experience severe external pressure due to muscle contractions and so it is also probable that stunning itself can cause the blood pressure problem (Lambooiji, 2004). Hot weather has been shown to also increase the incidence. Speckle is the rupture of blood vessels between the skin and the carcass and thus occurs in subcutaneous fat. This can arise when animals are exposed to long stun times or when

International Sheep and Wool Handbook

Processing of sheep and sheep meats 695 bleeding is poor and seems to be extenuated by inverted dressing systems. Stunning equipment should be checked to ensure that it is delivering the appropriate current or voltage according to the guidelines given above and those provided by the manufacturer. Decarbonising of the electrodes regularly with a wire brush will help to ensure good contact with the head of the animal.

Immobilisation

and Wichman, 1997). An example is the Y-cutting system, which handles the neck and foreleg section of the carcass. The Y-cutting system is comprised of a cutting device (knife based on 2 blades), a sensor system, an insertion device (insertion occurs at the hocks and the knife moves down the leg toward the vee of the neck) and a programmable robot. This region is also a major site of carcass contamination so robotics offer potential to limit the bacterial load on the carcass as the cutting head is sterilised between each animal.

The application of high frequency currents (2,000 Hz, 400 volts with a pulse width of 0.15 ms) has been shown extremely affective at reducing animal movement immediately after exsanguination. An example of this system is shown in Figure 30.6 with other systems applied to carcasses once on the chain. This reduces the risk of knife injuries due to relex movements. The evidence indicates that this application does not have any detrimental effect on meat quality, particularly pH (Toohey and Hopkins, 2007), thus enabling other electrical inputs further down the slaughter chain to be applied to either enhance bleeding or the rate of pH decline. Such immobilisation enables abattoir workers to safely begin processing sheep bodies (within 30 s) of exsanguination. Figure 30.7. Suspended sheep carcass showing the Y-cut. Source: E.S. Toohey. As shown in Figure 30.8 robotics can also be used to cut the brisket on an inverted chain, reducing labor and sources of contamination.

Figure 30.6. Immobilisation unit used immediately post exsanguination and before the carcasses are placed on the chain. Source: E.S. Toohey.

Pelt removal and dressing Most high throughput slaughter chains now use the inverted dressing system developed in New Zealand (see Figure 30.7). The cost of processing and hygiene considerations have driven this change as the system requires less slaughter men with a 40% reduction in labour for the same number of units (Devine and Gilbert, 2004) and reduces bacterial contamination (e.g carcasses with a surface count of bacteria above 104/cm2 reduce from 11% to 1%). This system is based on pelt removal from the neck region and front legs irst, with the carcass hung from the front legs. Automated (robotic) procedures for various sections of the dressing procedure have been developed in New Zealand (Templar

Figure 30.8. Inverted chain showing a robotic brisket cutter. Source: Peel Valley Exporters Tamworth (2008). Subsequent removal of the pelt from the middle of the back is usually performed manually with removal from the lower back and leg region by a puller (one example is given by Devine and Gilbert, 2004). Also, incorporated into this system is semiautomated head skinning and automatic front and rear hock removal. The irst phase of pelt removal is shown in Figure 30.8 where the pelt has been removed from the neck/forequarter region.

International Sheep and Wool Handbook

696 D.L. Hopkins The inverted system may increase the incidence of speckle and appears to increase the amount of “grain strain” - this is the cracking of the grain layer in skins and occurs in those areas of the skin where the pulling force is parallel to lines of tension. The lank area is the most easily damaged. The system also results in a higher rate of carcass downgrading than a traditional system where the carcasses stay suspended from the hindlegs during processing. The quality of dressing has a signiicant impact on the inal value of skins and particular attention needs to be paid to knife cuts during pelt removal. Cuts reduce the value of the resultant leather, make the skins unusable as rugs and often cause the skin to tear during tanning. Flay marks are less obvious but result in thin, weak areas.

Electronic bleeding With normal processing procedures, the expected yield of blood from a lamb carcass weighing 18 kg will be approximately 1.5 kg (Blackmore and Delany, 1988). A large proportion of this blood will be released in the irst two minutes post sticking. A study by Hopkins et al. (2006c) found that the application of a current of 600 mA, with a pulse width of 0.5 milliseconds and a frequency of 10Hz could increase the amount of blood collected soon after death by 30% and at 14Hz it could be increased by 11%. If the electrical current at 10 Hz was combined with a thoracic stick then the increase in collectable blood was 62% within 2 mins of death. With the widespread use of the inverted dressing system for sheep it is now possible to include a thoracic stick for the bleeding of sheep as a means of increasing the amount of blood captured in the bleeding area. A thoracic stick is achieved by a longitudinal incision which severs the major blood vessels in the vicinity of the heart. As part of the development of new electrical technology in Australia a commercial system to increase the collection of blood was produced. The system of electrodes is shown in Figure 30.7 with the current administered through the front legs. In this case the electrical parameters were 15 Hz, 550 peak volts, constant current of 800 mA, pulse width 0.5 milliseconds applied for 20 secs (Toohey et al., 2008a). Clearly for those abattoirs that sell blood meal there are improved proits to be realised from applying this approach. Additionally however, every gram of blood collected in the bleeding area reduces the amount of blood potentially present on the loor beneath the processing chain reducing what is an economic and environmental problem as it is hosed away as part of the overall loor cleaning program. Because this increases the Biological Oxygen Demand of the efluent, it is desirable that as much blood as possible be released into a deined bleeding area. The combination of a thoracic stick and electric current at 10 Hz would, based on the data presented by Hopkins et al. (2006c), potentially reduce the waste water in a 5,000 per day abattoir by 540kg. Furthermore, it could be expected that it would also reduce the amount of water required to hose the blood away.

Evisceration After pelt and hock removal, evisceration presents the major labour requirement of the lamb slaughtering system. Both brisket splitting (see Figure 30.8) and belly opening have been mechanised for current inverted systems. An automated brisket cutter and an automated eviscerator have also been developed. This has shown signiicant potential to reduce the labour requirement (up to 9 labour units/chain). Some of this is due to elimination of double handling of the viscera products during activities such as separation and trimming.

Meat inspection Ante-mortem (before death) inspection is usually carried out in the lairage on the morning of slaughter. The inspector looks for symptoms of any disease that could transmit disease to humans or other animals and render the meat unit for consumption. The qualiications of such inspectors vary between countries and within countries depending on the local regulations. No animals appearing to suffer from such a disease should be slaughtered for human consumption. Regulations vary according to country (e.g for Australia, see Anon, 2007a). During slaughter after the removal of the skin both the gastrointestinal tract and internal organs and the carcass are inspected for signs of disease (e.g. worms, jaundice, arthritis, pneumonia) and the contamination of carcasses is also assessed. If bruising or lesions are detected on the carcass they will be trimmed. In some cases samples of tissue are taken for detection of chemical residues with maximum residue levels applying to speciic chemicals. A major consideration is the reduction of bacterial contamination and good hygiene systems are required to limit the transfer of bacteria from the skin, faeces and humans to the carcass. The bacteria of concern for fresh meat are Salmonella spp., E. Coli and Campylobacter (Sofos, 2008) and it has been shown that Campylobacter is the most common food-borne pathogen of humans in a number of countries (Vanselow et al., 2007). Although feed withdrawal may reduce the load in the gastrointestinal tract and the bladder there is some evidence that it may actually increase the levels of bacteria such as E. Coli based on work in cattle (Gregory et al., 2000). A logical and systematic approach to reducing contamination is important and this involves the identiication of hazards, establishing the level of risk, identifying points where control can be implemented, selection of control options and monitoring the control. This approach is termed ‘Hazard Analysis Critical Control Points’ (HACCP). Shearing before slaughter does not appear to be an effective method for reducing contamination (Sheridan, 1998). Several control options exist to reduce contamination levels: 1) hot water ≥80°C must be used to decontaminate knives and viscera inspection systems, 2) trimming visible contamination, 3) steam vacuuming (Figure 30.9) and 4) washing with water (Koutsoumanis and Sofos, 2004). Hot water washes are more effective at reducing bacterial load (Sheridan, 1998).

International Sheep and Wool Handbook

Processing of sheep and sheep meats 697

Figure 30.9. Steam vacuuming system to remove visible contamination from the hindlegs. Source: Peel Valley Exporters Tamworth (2008).

Carcass measurement

Figure 30.10. Measurement of GR on the chain with the AUSMEAT sheep probe. Source: D.L. Hopkins.

Methods of measurement

capable of measuring GR within 2 mm of actual values in 90% of carcasses operating at a chain speed of up to 9 carcasses per minute (Hopkins et al., 1995a). The probe has a sharp blade, which cuts through the tissue, until it lodges on the rib bone and the depth is measured by displacement. Although other sites on the carcass may give better predictions of composition or meat yield (Hopkins et al., 2007a) the dificulty of measuring them negates their value. There has been some development of alternative systems to measure carcasses at chain speed and work by Stanford et al. (1998) conirmed that a video image based system had potential to replace existing systems used in Canada which were designed to predict yield and which relied upon a human. This followed work in the UK by Horgan et al. (1995) on a non-commercial video imaging system which suggested that this technology had the potential for predicting commercially important features of lamb carcasses. A commercial system (VIAScan®) was developed in Australia that could predict lean meat yield more accurately than a system based on carcass weight and GR (Hopkins et al., 2004), but it could not measure GR with the same accuracy as the AUS-MEAT sheep probe. VIAScan technology was used in 2 Australian abattoirs and several in New Zealand by 2009, but the cost has prevented wider adoption. Dorsal images

There is no international carcass grading or measurement system for sheep and lamb carcasses, but for those systems that do exist they are either based on subjective assessments of fat cover and conformation or objective measures taken on the carcass. In the European Union the former approach is taken (de Boer, 1992) and this uses 5 conformation classes (EUROP) with E being the best conformed and P the least. There are also 5 fat classes (1-5) with 5 being the fattest and within classes 3 and 4 subdivisions into high and low levels. In New Zealand there are 3 export classes (A = devoid of external fat, Y = low fat and P = medium fat). Excessive fat is trimmed and this gives rise to 3 other classes (Anon, 2003). Superimposed over this are 4 carcass weight grades and within some combinations there is further grading for muscling in response to the introduction of the Texel breed (Waldron et al., 1992). The New Zealand system bases the fat classes on the measurement of GR tissue depth. This is the total tissue depth over the 12th rib, 11 cm from the midline of the carcass. In Australia the measurement of GR has also been adopted and this can be measured with a specially designed knife or the AUS-MEAT sheep probe (Figure 30.10). The sheep probe has been found

International Sheep and Wool Handbook

698 D.L. Hopkins are interrogated by a computer program which uses prediction models to provide estimates of traits like lean meat yield. The commercial development of VIAScan® has provided the potential for an objective assessment of features such as conformation and fat cover, but also allows prediction of primal weights which has been utilised to streamline boning room operations. The system records dimensional measures, areas and colour measures and the installation on the chain is shown in (Figure 30.11). Other technologies such as impedance (Hegarty et al., 1998) and electromagnetic scanning (Wishmeyer et al., 1996) have been investigated, but not applied commercially for measurement of sheep and lamb carcasses on-line. There is some interest in applying fast speed CT scanning to carcasses, but this is in early stages of investigation and currently processing speeds are not fast enough for on-line application Kongsro et al. (2008).

on a 5 point scale or in percentage terms in combination with fat and muscle depth measures. In fact the evidence indicates that use of the weight of muscle and subcutaneous fat from the loin cut can lift the level of accuracy to 76% (Hopkins, 2008). Workable systems to capture this type of data in commercial boning rooms remain a challenge.

Application of measures Collection of carcass data can be used to streamline processing, speciically boning, provide feedback to livestock buyers and be used as the basis of payment to producers. In Australia to aid this process a carcass ticketing system was developed. Carcass weight and fat score (or GR in millimetres) information is captured electronically and this is printed on the ticket with kill date, lot number and chiller destination information (Figure 30.12). This information is then summarised on feedback sheets that show average carcass weight and fat score for each lot which can be sent back to producers. The carcass ticket provides processors, wholesalers and retailers with information that can be used to; •฀ •฀ •฀ •฀

Provide an estimate of the yield of saleable meat Indicate the level of trimming required Determine the post-mortem age of the carcass Determine the sex and dentition (if printed)

Operators such as wholesalers who purchase sight unseen can also use the ticket to verify that their purchases from a processor are according to their speciications.

Chilling, freezing & boning

Figure 30.11. The video camera is located in the semi enclosed compartment and a stationary black back drop (left of photo) is used for contrasting the carcass. Source: D.L. Hopkins. Recently, however in Australia, the concept of tracking speciic cuts through a boning room and collecting data on those cuts has been under investigation, with the aid of electronic tracking systems. The concept is based on the fact that the VIAScan® system only predicts lean meat yield with approximately 55% accuracy and previous work by Kempster et al. (1986) suggested that predictive accuracy could be improved by the use of subjective estimates of subcutaneous carcass fat either

Chilling regulations vary between countries, but the purpose of chilling is generic – reduction in body temperature to prevent undesirable bacterial growth so as to protect human health. Manipulation of chilling regimes and holding temperatures is undertaken to maximise shelf life in terms of colour display and bacterial growth. Aerobic Pseudomonas species are the dominant bacteria responsible for spoilage at chill temperatures (Newton and Gill, 1980-81). Pseudomonas utilise glucose in preference to other substrates and then degrade amino acids.

Chilling Chilling is the process of cooling meat while the meat remains above its freezing temperature. The temperature of the cooling medium (air or water, for instance) doesn’t matter and the lower the temperature the slower is bacterial growth and the chemical reactions that take place post-mortem. Chilling serves to transfer heat from carcasses and offal to other objects. Of the mechanisms of heat transfer the refrigeration process involves combinations of conduction and convection and Lovatt (2004) provides a detailed

International Sheep and Wool Handbook

Processing of sheep and sheep meats 699 Operators number

Abattoir identification Sequential body number

Date of slaughter

Lot number

Category of stock (in this case lamb)

Weight class

Fat depth (GR mm)

Fat score

Figure 30.12. A carcass ticket showing the type of information which is recorded. Source: D.L. Hopkins. description of the importance of these factors for chilling. To chill carcasses the temperature must be lower than the surface temperature and forced convection (from fans) carries heat away from the surface more quickly which is replaced by internal heat through conduction until the temperature of the carcass equilibrates with the surrounding temperature. Carcass surfaces dry as they chill and humidity and air low both inluence drying. Drying is an important part of microbial control (Bell et al., 1988), but it also results in weight loss from carcasses. Rapid chilling in the early part of the chill cycle gives good microbial control and low weight loss. This can however produce tough meat through “cold shortening” and also dry the surface degrading the appearance. Also, if chillers are pre-cooled before they are loaded; to aid rapid chilling, condensation will form on overhead structures. Commonly much water is sprayed onto the carcass during dressing to satisfy regulations, but this does not remove bacteria and instead spreads them over the carcass. Minimising the use of water will limit bacterial spoilage and help to reduce condensation in chillers. Chilling requirements for sheep and lamb carcasses in Australia are given below (Anon 2007a), but these vary according to country. There are separate conditions for hot boning of carcasses.

the major health objectives are achieved while weight loss and damage to meat quality is minimised. There is no single set of optimum chilling conditions but the following points were outlined by Hopkins et al. (1996);

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Air movement in the chiller should be uniform. Ideally the air velocity over carcasses should be about 0.5 to 1 m/s in the early part of chilling, but the air velocity can be reduced to 0.2 m/s in the later stages for storage of chilled lamb. The air velocity off the face of the evaporators should be no more than 4 m/s.

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Carcasses must be spaced in the chiller so that there is air movement over all surfaces. Touching surfaces cool slowly and do not dry. They provide ideal conditions for microbial growth.

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At the start of loading a chiller, the chiller air temperature (and chiller surfaces) should be at or above the temperature that can be maintained during loading. Typically the air temperature during loading is 5–10°C. If the chiller is pre-cooled below 5oC and the air temperature rises during loading, condensation will occur.

All carcasses must be placed under refrigeration within 2 hours of stunning. Surface temperatures of carcasses, sides and quarters shall be reduced to 7°C within 24 hours of stunning.

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Chilling conditions vary depending on what temperature is required in what time. Fast chilling rates are needed if, for example a load-out temperature of 7oC must be achieved within 12 hours of slaughter.

A range of chiller temperatures for sheep carcasses applied commercially from –2°C to 8°C has been reported, with more variation within export abattoirs (Hopkins, 1993). Some works use several different chilling programs. Export works producing a chilled product were characteristically using temperatures below 2°C for export product (Hopkins, 1993). If product was to be boned for the local market, higher temperatures were used. Abattoirs operating chillers at