Genotype and age effects on sheep meat production 2. Carcass quality traits
E. N. Ponnampalam A B F , D. L. Hopkins D , K. L. Butler C , F. R. Dunshea B E and R. D. Warner BA Australian Sheep Industry Cooperative Research Centre, Armidale, NSW 2350, Australia.
B Animal Production Sciences Platform, Department of Primary Industries, 600 Sneydes Road, Werribee, Vic. 3030, Australia.
C Science Innovation and Quality, Department of Primary Industries, 600 Sneydes Road, Werribee, Vic. 3030, Australia.
D NSW Department of Primary Industries, Centre for Sheep Meat Development, PO Box 129, Cowra, NSW 2794, Australia.
E Present address: The University of Melbourne, Parkville, Vic. 3010, Australia.
F Corresponding author. Email: eric.ponnampalam@dpi.vic.gov.au
Australian Journal of Experimental Agriculture 47(10) 1147-1154 https://doi.org/10.1071/EA07001
Submitted: 12 January 2007 Accepted: 5 April 2007 Published: 19 September 2007
Abstract
The present study examines carcass quality traits in different genotypes of Australian sheep slaughtered at 4, 8, 14 and 22 months of age. Poll Dorsetgrowth × Border Leicester Merino (PDg × BLM), Poll Dorsetgrowth × Merino (PDg × M), Poll Dorsetmuscling × Merino (PDm × M), Merino × Merino (M × M) and Border Leicester × Merino (BL × M) genotypes were compared. Sires were selected on the basis of growth (PDg, M and BL) and muscle (PDm) using estimated breeding values (EBVs). Approximately 150 mixed sex animals were slaughtered at each age (595 in total for the four slaughters) and carcass quality traits, including hot carcass weight, loin and semitendinosus (ST) muscle weights, GR fat, fat C, rump fat depth and eye muscle area (EMA), were determined at 45 min to 3 days postslaughter. With age, all carcass quality traits increased in magnitude. Merinos produced the lightest and leanest carcasses (P < 0.01) with lowest values in nearly all the carcass quality traits. At 4 and 8 months of age carcass and loin weights, EMA and GR fat measures were greater (P < 0.01) in second-cross PDg × BLM sheep than all other genotypes. However, traits related to muscle content were similar between first- and second-cross Poll Dorset genotypes at 14 and 22 months of age. The BL × M genotype had lower values than the PD × M genotypes for these traits, at all ages. Traits related to carcass fatness showed that sheep with Border Leicester genetics tend to deposit more fat (P < 0.001) in the carcass than those with Merino or Poll Dorset genetics from 14 months of age onwards. Most carcass quality traits did not differ (P > 0.05) between first-cross Poll Dorset genotypes selected for growth or muscling (PDg × M v. PDm × M). Sires with high muscling EBVs are associated more with shorter carcass length than low muscling EBVs. From ~8 months of age, wethers had greater values (P < 0.05) than ewes of the same age for most carcass quality traits related to size and muscle development, but no effect was present for carcass quality traits that were related to fat deposition. It was clear that the carcass weight of M × M at 8 and 14 months were similar to that observed in PDg × BLM at 4 and 8 months, respectively. Loin weights of M × M and BL × M at 13 and 8 months were similar to that weights observed in PDg × BLM at 8 and 4 months of age, respectively. Animals slaughtered to a muscle weight specification will reach the target at a younger age when they have more Poll Dorset than Border Leicester background genetics. Alternatively animals slaughtered at a specified fat score (using fat C or rump fat depth) will reach the specification at a younger age when they have more Border Leicester than Poll Dorset genetics.
Acknowledgements
Technical support for this study was provided by 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 (University of New England), Peter Allingham (CSIRO) and Tracy Lamb and Rachel McGee funded by CSIRO, Drs Danny Suster and Matt McDonagh, Matt Kerr, 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 Uni). The excellent co-operation of employees and management from Junee Abattoir is gratefully acknowledged. The study was funded by Meat and Livestock Australia, Department of Primary Industries, Victoria and the Australian Sheep Industry Cooperative Research Centre. Dr Arthur Gilmour is thanked for his statistical advice over a complex data analysis.
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