Sire and growth path effects on sheep meat production 2. Meat and eating quality
D. L. Hopkins A B F , D. F. Stanley B , E. S. Toohey C , G. E. Gardner D , D. W. Pethick D and R. van de Ven EA Australian Sheep Industry Cooperative Research Centre, Armidale, NSW 2350, Australia.
B NSW Department of Primary Industries, Centre for Sheep Meat Development, Cowra, NSW 2794, Australia.
C NSW Department of Primary Industries, Dubbo, NSW 2830, Australia.
D Murdoch University, Perth, WA 6150, Australia.
E NSW Department of Primary Industries, Orange Agricultural Institute, Orange, NSW 2350, Australia.
F Corresponding author. Email: David.Hopkins@dpi.nsw.gov.au
Australian Journal of Experimental Agriculture 47(10) 1219-1228 https://doi.org/10.1071/EA06334
Submitted: 19 December 2006 Accepted: 2 May 2007 Published: 19 September 2007
Abstract
The meat and eating quality characteristics of 627 crossbred lamb progeny from 20 Poll Dorset sires were studied. The sires were selected on the basis of Australian sheep breeding values (ASBVs) for postweaning growth (PWWT), depth of loin muscle (PEMD) and subcutaneous fat (PFAT). Lambs were either weaned at 20- or 30-kg liveweight and then within each of these groups held at their weaning weight for 55 days or fully fed, giving four treatment groups. Restricted lambs were realimentated subsequent to the period of feed restriction and the lambs within each treatment group were slaughtered when their mean liveweight reached 45 kg. Shear force of the M. longissimus thoracis et lumborum (LL) decreased with temperature at pH 6.0, increased with LL ultimate pH and decreased as sarcomere length increased. Within LL aged for 5 days there was no difference between (P > 0.05) between treatments for shear force. There was a treatment effect on M. semimembranosus (SM) shear force, such that for a sire having an average ASBV PWWT of 9.34, topsides from lambs early weaned and restricted had significantly (P < 0.05) lower values. Further within these same lambs, i.e. early weaned and restricted, as the sire ASBV PWWT increased there was a significant (P < 0.001) reduction in shear force. There was a significant (P < 0.05) increase in sensory tenderness as the sire ASBV PFAT increased and across the range of ASBV PFAT this represented a change in sensory tenderness of four points. Overall liking increased with an increase in the temperature at pH 6.0 (P < 0.05) with a coefficient of 0.43 ± 0.19. There was a significant (P < 0.05) interaction between feeding level and the sire ASBV PFAT, such that for restricted fed lambs overall liking increased as the ASBV PFAT increased (coefficient 2.80 ± 0.89) after adjusting for temperature at pH 6.0, but this is not the case for fully feed lambs (coefficient –0.01 ± 0.89). Subtle interactions between sire ASBVs and growth path suggest that the impact of a period of restriction and refeeding on meat and eating quality will be meditated by the sire genetics.
Acknowledgements
Technical support for this study was provided by Leonie Martin, Tony Markham, Jayce Morgan, Andrew Roberts, Megan Moppett, Tracy Lamb, Geoff Casburn, Brent McLeod, Joe Brunner and Stuart McClelland (NSW Department of Primary Industries), Andrew Slack-Smith and Jason Siddell (University of New England), Peter Allingham (CSIRO), Dr Matt McDonagh, Peter Walker, Matt Kerr, Dete Hasse, Matt Knight, Erin Rutty, Paul Eason and Fahri Fahri (DPI, Victoria), Dr Greg Nattrass and Victoria Ferris (SARDI), Mal Boyce and Grace Chan (Murdoch University), Dr Robin Jacob (DAWA) and Linden Cowper, Janine Lau, Nathan Sheahan and Colin Cowell (MSA). Testing of samples for shear force and intramuscular fat was undertaken by the meat science section at the University of New England. Determination of MFI and ultimate pH was conducted in the ISO 2001 accredited laboratory at the Centre for Sheep Meat Development, Cowra. The preparation and imaging of samples for histology was undertaken by the staff of CELLCentral, School of Anatomy and Human Biology, University of Western Australia and this is gratefully acknowledged. Thanks to Dr A. Ball (MLA) for providing the sire recommendations and to the breeders who allowed the purchase of semen. The excellent cooperation of Junee Abattoir employees and management is gratefully acknowledged. The study was funded by NSW Department of Primary Industries, Meat and Livestock Australia and the Australian Sheep Industry Cooperative Research Centre.
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