Genotype and age effects on sheep meat production. 5. Lean meat and fat content in the carcasses of Australian sheep genotypes at 20-, 30- and 40-kg carcass weights
E. N. Ponnampalam A B E , K. L. Butler B , D. L. Hopkins C , M. G. Kerr B , F. R. Dunshea B D and R. D. Warner BA Australian Sheep Industry Cooperative Research Centre, Armidale, NSW 2350, Australia.
B Department of Primary Industries, 600 Sneydes Road, Werribee, Vic. 3030, Australia.
C New South Wales Department of Primary Industries, Centre for Sheep Meat Development, Cowra, NSW 2794, Australia.
D Present address: The University of Melbourne, Melbourne, Vic. 3010, Australia.
E Corresponding author. Email: eric.ponnampalam@dpi.vic.gov.au
Australian Journal of Experimental Agriculture 48(7) 893-897 https://doi.org/10.1071/EA08054
Submitted: 24 January 2008 Accepted: 16 April 2008 Published: 20 June 2008
Abstract
Lean meat and fat content of Australian sheep genotypes were compared at 20-, 30- and 40-kg carcass weights. Sheep comprised Poll Dorsetgrowth × Border Leicester Merino (PDg × BLM), Poll Dorsetgrowth × Merino (PDg × M), Poll Dorsetmuscling × Merino (PDm × M), Border Leicester × Merino (BL × M) and Merino × Merino (M × M) genotypes. Lambs were raised as a mixed flock under grazing and slaughtered at 4, 8, 14 and 22 months of age with each slaughter time involving ~150 mixed sex animals. At 24 h after slaughter, chilled carcasses were halved along the backbone and the right sides were used for determination of lean, fat and ash percentages using dual energy X-ray absorptiometry. Within a particular age group and genotype, animals growing at faster rates and reaching heavier carcass weights had lower carcass lean meat content than slower growing animals. Merino carcasses weighing 20 and 30 kg had similar levels of lean meat to PD × M genotypes, which was greater than that from the BL × M genotype. Second-cross PD × BLM carcasses weighing 20 kg at 4 months and 30 kg at 8 months had similar carcass fat and lean percentages to 20-kg Merino carcasses at 8 months and first-cross PD × M carcasses weighing 30 kg at 14 months, respectively. At 40-kg carcass weight, 22-month-old Merinos had similar levels of leanness to carcasses from 22-month-old PD × M animals and carcasses from 14-month-old second-cross PD × BLM animals. Carcass lean meat content decreased with increasing carcass weight and first- cross BL × M animals had the lowest carcass lean across all weight categories. There was a major acceleration in carcass fatness between 14 and 22 months associated with a reduction in muscle deposition. Results indicate that age of the animal should be taken into account when carcass lean and fat contents are compared at a particular carcass weight. Merinos will achieve weight/composition specifications at least equally well to crossbreds but will take longer with a likely increase in production costs.
Acknowledgements
The study was funded by Meat and Livestock Australia and the Australian Sheep Industry Cooperative Centre. The excellent cooperation of Junee Abattoir employees and management is gratefully acknowledged. Technical support for this study was provided by David Stanley, Leonie Martin, Edwina Toohey, Tony Markham, Jayce Morgan, Andrew Roberts, Sally Martin, Brent McLeod, Steve Sinclair, Joe Brunner, Stuart McClelland and Amanda Lang (NSW Department of Primary Industries), Kirstie Martin and Kirsty Thomson (formerly University of New England), Peter Allingham (CSIRO) and Tracy Lamb and Rachel McGee funded by CSIRO, Drs Danny Suster and Matt McDonagh, Dete Hasse, Oliver Fernando, Erin Rutty, Paul Eason and Fahri Fahri (DPI, Victoria), Dr Greg Nattrass (SARDI) and Dr Martin Cake and Mal Boyce (Murdoch University).
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