Selection for increased visual muscling increases carcass leanness without compromising predicted Meat Standards Australia eating-quality index

B Walmsley1, L Cafe2, J Wilkins2, M McPhee2

1Animal Genetics and Breeding Unit, University of New England; 2New South Wales Department Of Primary Industries

Selection using visual muscle score (MSc) at weaning has been proposed to increase meat yield. Data were collected on one cohort of steers (n = 67) from a herd established to examine the effects of MSc and the myostatin mutation (821del11) on both commercial and compositional carcass traits. One copy of the myostatin mutation was found to have large effects on Computed Tomography (CT) scanned carcass composition with increased lean tissue percent (lean, %) (P < 0.01), decreased fat tissue percent (fat, %) (P < 0.05) and increased lean:bone ratio (P < 0.01). One copy of the myostatin mutation also affected carcass traits with decreased P8 rump fat (mm) (P < 0.05) and Meat Standards Australia (MSA) marble score (P < 0.05). In steers without the myostatin mutation, increases in MSc between low and high muscling cattle were associated with increases in carcass lean and decreases in carcass fat, along with smaller changes in P8 rump fat (P = 0.78), MSA marble score (P = 0.12) and MSA index (P = 0.24). These results suggest that MSc could be used to increase carcass yield without negatively affecting meat quality.


Malcolm McPhee obtained his Bachelor of Applied Science (Mathematics) from the University of Technology Sydney (1982), Master of Statistics from University of Wollongong (1995) and PhD in Nutritional Biology majoring in Animal Systems Modelling from the University of California, Davis, USA (2006). He has worked for NSW DPI for over 25 years and is currently in the extensive livestock unit, Armidale.
Malcolm has led a team of extension staff and researchers to develop a Northern Tablelands version of SheepO, ProPlus a fodder budgeting package for ProGraze courses and a drought workshop titled StockPlan that includes 3 decision support tools (Drought Pack, FSA Pack, and ImPack). More recently, Malcolm has led a team researching fat deposition in beef cattle which has led to the development of the BeefSpecs Fat Calculator, BeefSpces Drafting Tool and BeefSpecs optimisation tools for feedlots and pasture based systems. The fat deposition research has also led to the development of a partnership with the University of Technology Sydney in using 3D camera technology to assess P8 fat (mm) and muscle score in cattle. Malcolm has also led an international team to integrate sheep and beef rumen models into a whole-farm system to evaluate methane mitigation strategies.

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