Data from 95 lamb carcasses (2 data sets) and 90 bull carcasses were used to examine relationships between objective measures of carcass muscling and subjective scores of muscularity or conformation. Objective indexes calculated for lamb carcasses included muscle to bone ratios (M:B), muscularity indexes (MUSC) for both the leg and the whole side, the ratio of eye muscle depth to width (B:A), weight-adjusted eye muscle area and carcass weight per unit length. Similar variables were calculated for beef carcasses except that the weights of three commercial leg cuts were used in place of dissected muscle weights. Leg MUSC had the closest relationships with subjective scores of muscularity or conformation (R2% = 69 to 80% for lambs and 56% for bulls), with leg M:B being only slightly inferior (R2% = 62% for lambs and 652% for bulls). Side MUSC or M:B were the next best as predictors, but variables based on the eye muscle were poor. Carcass weight per unit length showed close relationships with subjective scores in some cases but its usefulness is limited by the fact that it can be influenced by fatness and is breed related. These results support the contention that measures of M:B may not always reflect muscularity scores because they are based on weights rather than depths and lengths. It is concluded that the objective measures of MUSC used here reflect subjective scores satisfactorily, given that subjective scores have limitations with respect to repeatability. MUSC based on the femur and the muscles or cuts surrounding it, in particular, may constitute a useful objective standard for use in the industry.

HG, Judson, and AM Nicol

Proceedings of the New Zealand Society of Animal Production, Volume 53, , 339-342, 1993
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