A survey to assist development of carcass description and live assessment systems for goats.

Abstract

Proc. Aust. Soc. Anim. Prod. Vol. 19 A SURVEY TO ASSIST DEVELOPMENT OF CARCASS DESCRIPTION AND LIVE ASSESSMENT SYSTEMS FOR GOATS P. L. GREENWOODA, J. A. FINNA and T, J. MAY B 'NSW Agriculture, Elizabeth Macarthur Agricultural Institute, Menangle, N.S.W. 2568. BNSW Agriculture, Dubbo, N.S.W. 2860. SUMMARY A survey was conducted to obtain data on live assessment, carcasses, yields of meat and other components for over 1000 goats representative of ages, types, sexes, liveweights and live assessment scores encountered in Australia. The methodology for this survey and initial results which provide an overview of the data set are presented. The data should allow for creation of models to aid in the development of live assessment and carcass description systems for goats and prediction equations for characteristics of economic importance. Results from the survey should therefore assist development of a mechanism to translate market-related information to goat producers in an objective way. Keywords: carcass description, live assessment, goats. INTRODUCTION Australia exported 10 582 tonnes of goat meat during the year ended June 1991 (Anon. 1991) making it the largest exporter of goat meat in the world. However, these exports represent only 1.0% of meat exported from Australia. Existing export markets mainly utilise lean whole carcasses of feral origin which may result in poor financial returns, and demand for which is influenced by the availability of cheap alternatives. Domestic and export markets for high quality goat meat have been identified, and the opportunity exists to supply a broad range of consumers, both locally and abroad (Greenwood 1985). Further development of domestic and export markets is likely to require improvements in economically important goat carcass characteristics. A prerequisite to such improvements is the establishment of a mechanism by which market-related information can be accurately and objectively translated to, and be used by, industry. Such a mechanism would also allow for marketing with pricing systems based on objective measurements to be introduced. Goat carcass characteristics of economic importance may include subcutaneous fat coverage, carcass conformation and muscularity, and meat colour (Devendra and Owen 1983; Colomer-Rocher et aZ. 1987). As a first step towards development of more objective carcass description and live assessment systems for goats, which are closely related to economic characteristics, and to obtain information on yields of carcass and animal components, a survey was undertaken. Here we describe the investigation and initial results of the survey. MATERIALS AND METHODS Animals were selected according to type (Angora, cashmere, dairy, feral and meat), age as determined by dentition, and sex (female, entire male, castrate male). Goats were obtained from commercial enterprises except for meat-type goats which were obtained from a herd at Condobolin developed by New South Wales Agriculture (Mitchell 1977). Liveweights and general body condition were specified in an attempt to include goats representative of the range of animals available commercially. Goats were transported to, and arrived at, abattoirs on the day prior to slaughter, and were individually identified at all stages of data collection. Type, sex, dentition, and fleece and horn characteristics were recorded in order to characterise animals. Goats were weighed and live assessment scored to estimate the degree of muscularity and fat cover, approximately 2 h prior to slaughter. The live assessment methods were as follows: (i) Cl, a l-7 score based on palpation to determine the shape of the M. longissimus dorsi and the degree of fleshing over the processes of the vertebrae in the lumbar region. This method was as described by Honhold et al. (1988), except that whole numbers, rather than a l-4 system with half scores, were used; (ii) C2, a 14 score based on palpation of the processes of the vertebrae in the lumbar region to determine the degree of fleshing over them (Mitchell 1986); (iii) C3, a l-5 score based on palpation of the long ribs and of the vertebrae in the lumbar region to determine the degree of fleshing over them (May et aZ. 1987); (iv) C4, an estimate of GR-site (110 mm from the carcass mid-line over the 12th rib; Anon. 1989a) tissue depth in mm; 277 Proc. Aust. Sot. Anim. Prod. Vol. 19 (v) palpation of sternal fat (Santucci and Maestrini 1985). This proved impractical and was not assessed further following preliminary investigation. Most carcasses were prepared in accordance with the AUS-MEAT standard carcass (Anon. 19893). Measurements of the kidneys, kidney knob and channel fat were made in order to standardize data to the AUS-MEAT standard where necessary. Carcasses were weighed hot (within 2 h of slaughter) and cold (24 h after hot carcasses were weighed). Dressing percentages and meat yields were derived using the hot standard carcass weight (HSCW). Where practicable, weights of heads, skins, offal, and, if present, foetuses and foetal fluids and membranes were obtained. Linear measurements were made using methods described by Palsson (1939). These included leg length (f), body length (k), width of thighs (g), thorax depth (Th). In addition, thorax and thigh circumferences were measured. Tissue depths were measured at the GR-site (using a GR-knife; Anon. 1989a) to assess subcutaneous tissue depth, and at 3 sites along the M. longissimus dorsi termed Ll, L2 and L3, which were developed during preliminary investigations. Of the latter measures, L2 (which is a measure of muscle development) proved the most practical and useful. L2 is the total tissue depth over the first lumbar vertebra 35 mm from the mid-line measured using a probe which forms part of a vernier calliper. The probe is inserted through the M. longissimus dorsi parallel to the dorsal process of the vertebra until it hits the lateral process. The score is read from the calliper. Tissue depth measured at the C-site (Palsson 1939) was also investigated during preliminary work. This proved unsatisfactory because it was not possible to obtain a reading on many carcasses due to a lack of fat cover over the M. longissimus dorsi. Eye muscle area was determined using a planimeter, from tracings of cross-sections of M. longissimus dorsi made after removal of these muscles from carcasses. Meat colour was assessed on the inside of the M. rectus abdominus using colour grading chips (score l-7: 1, very pale pink/brown; 7, very dark red-brown) developed for beef and veal by the Department of Agriculture and Rural Affairs in Victoria. The range of colours for the grading chips was deemed satisfactory for goat carcasses. Meat yield data were obtained in commercial boning rooms within 48 h of slaughter, by sequentially boning each carcass into bone-in chump-on legs, boneless chump-on legs, backstraps, and total boneless meat, in accordance with the Sheep, Meat Section of the Handbook of Australian Meat (Anon. 1986). Intercostal muscles were not removed from the thoracic cage, and saleable meat was determined as the weight of total boneless meat following trimming to remove excessive fat. Carcasses were also allocated to a market category (Greenwood 1985) based on the following specifications: (i) Prime kid: milk-tooth, HSCW less than or equal to 14 kg, and colour score 1,2 or 3, (ii) Young goat: milk-tooth or 2-tooth, HSCW less than or equal to 20 kg, colour score greater than 3 if milk-tooth and HSCW less than 14 kg, (iii) Goat: all other carcasses. All analyses were performed using REG (Gilmour 1985). RESULTS A summary of the data is presented in Table 1. In total, data from 1014 goats and goat carcasses were obtained. Numbers of goats according to categories were: (i) type: angora 357, cashmere 136, dairy 52, feral 237 and meat 232; (ii) age: milk-tooth 513,2-tooth 112,4-tooth 79,6-tooth 93 and full-mouth 217; (iii) market category: prime kid 388, young goat 233 and goat 328. DISCUSSION The survey described here is among the most comprehensive undertaken on goats and goat meat. It is possibly the first specifically designed to assist development of live assessment and carcass description systems based on objective assessment, in which an attempt to include the range of goats within a goat meat industry was made. This data set should assist to improve live assessment (Mitchell 1986) and carcass description systems (Anon. 1989b) for goats currently in use in Australia, and in more subjective systems (Colomer-Rocher et al. 1987). Creation of models from the data should allow for development of prediction equations for characteristics of economic importance, such as yields of saleable meat (or muscularity) or subcutaneous fat/tissue depth, which incorporate independent variables including type, dentition and sex. In addition, the data should allow for development of similar models for each market category, and statistics for yields of various carcass and animal components should provide valuable information for the goat meat industry. Although further research is required to assess effects of pre-slaughter management on goats and goat carcasses, this data set should assist establishment of an objective method to translate market-related information to producers and should therefore help development of the goat meat sector in Australia. 278 Proc. Aust. Sot. Anim. Prod. Vol. 19 Table 1. Mean k s.d. and ranges for measured and derived live animal, carcass, boning and other parameters obtained by surveying the goat meat industry in New South Wales HSCW, hot standard carcass weight 279 Proc. Aust. Sot. Anim. Prod. Vol. 19 ACKNOWLEDGMENTS Financial assistance provided by the Meat Research Corporation to conduct this project (DAN 041) is gratefully acknowledged. The authors also wish to thank other officers of NSW Agriculture who participated in the study, in particular, Mr B. Turner, Mr E. Scarlett, Dr R Holst and Mr C. Allen, and various Departmental staff who assisted with selection, handling and transport of goats. The kind assistance provided by numerous suppliers of goats, and Wilberforce, Mirrabooka and Wollondilly abattoirs and associated boning establishments is also acknowledged. We also wish to thank The University of Sydney who allowed us to utilise facilities at the M.C. Franklin Laboratory, Camden during preliminary work, and Mr R Nicholls who provided considerable biometrical advice. REFERENCES ANON. (1986). ` Handbook of Australian Meat.' 4th Edn. (Australian Meat and Live-Stock Corporation: Sydney.) ANON. (1989a). ` AUS-MEAT Operations Manual' 2nd Edn. (AUS-MEAT: Sydney.) , ANON. (1989b). ` AUS-MEAT Language' 3rd Edn. (AUS-MEAT: Sydney.) , ANON. (1991). ` Summary of Australian Meat and Livestock Statistics, June 1991' (Australian Meat and LiveA . Stock Corporation: Sydney.) COLOMER-ROCHER, F., MORAND-FEHR, P. and KIRTON, A. H. (1987). Lives. Prod. Sci. 17: 149-59. DEVENDRA, C. and OWEN, J. E. (1983). World Anim. Rev. 47: 19-29 GILMOUR, A. R. (1985). ` REG - A Generalised Linear Models Program' Miscellaneous Bulletin 1. (Department . of Agriculture, NSW: Sydney.) GREENWOOD, P. L. (1985). ` Some Aspects of the Australian Goatmeat Industry' Commodity Bulletin 14: 1-15. . (Department of Agriculture, NSW: Sydney.) 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