Estimation of the carcass composition of different cattle breeds and crosses from conformation assessments adjusted for fatness

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Abstract
SUMMARY: Carcass data for 1053 steers from the Meat and Livestock Commission's beef breed evaluation programme were used to examine the prediction of carcass composition from conformation-related characteristics corrected to equal fatness. The data were from four trials and comprised both dairy-bred and suckler-bred cattle by a wide range of sire breeds.When used with carcass weight (W) and a visual assessment of carcass subcutaneous fat percentage (SFe) (the most precise simple assessment of carcass lean percentage, residual S.d. = 2·28), m. longissimus area (MLA) at the 10th rib was the most effective conformation-related assessment (residual S.d. = 2·10). Precision was improved by the further addition of a visual conformation assessment (C15) on a 15-point scale (residual S.d. = 2·06). The use of equations combining W, SFe, MLA, C15 and other simple assessments of fatness improved the precision further (residual S.d. = 1·94).The measurement combinations above also provided a significant prediction of the percentage of total carcass lean distributed in the higher-priced joints. Residual S.d.s were: W + SFe, (1·12); W + SFe + MLA (1·07); W + SFe + MLA + C15 (1·06).When the equations were applied to the breed means, there was substantial bias (predicted – actual carcass lean percentage). Bias ranged from approximately + 1·5 (purebred Canadian Holsteins and Luings ) to – 1·6 (Limousin crosses). The accuracy of carcass lean prediction was not improved by the addition of bone measurements to the equations but there was some improvement in the prediction of lean to bone ratio: cattle with light, thin bones tended to have higher ratios.Similar combinations of independent variables were found to provide the most precise prediction within breed.