Prediction of lean content in the carcasses of beef cattle. I. From measurements of wholesale carcasses

Abstract

Carcass data on 304 steers and 320 heifers from seven breed of dam groups were analyzed to test equations designed to predict lean content as weight and proportion in beef carcasses from measurements of the wholesale carcasses. Measurements included cold-carcass weight (CW), average backfat (AB) thickness, longissimus muscle (LM), semimembranosus (SM), semitendinosus (ST) and biceps femoris (BF) muscle areas, hip weight, marbling and other quality scores as indirect measures of composition. Actual lean weights and proportions were obtained from physical separation of fat, lean and bone from one side of the carcass. Prediction equations were obtained from the overall data and subpopulations by breed of sire–degree of finish combination, by sex and by breed of dam group. For predicting lean weight in the carcass, CW, LM and AB were the most important predictors. Addition of hip weight, SM and ST improved both precision and accuracy. For predicting proportion lean in the carcass, the addition of hip percentage, SM and ST to CW, LM and AB improved precision. The overall equation including these six independent variables supplied precise estimates (r2 of 0.93–0.97) of lean weight with little bias (average biases of −0.54 to 0.41 kg) for all subpopulations. Important biases in predicting lean proportion were observed from some breed of dam groups, indicating that an equation derived from an overall population cannot be used without error for all subpopulations of breed of dam groups. Key words: Beef, carcass, prediction, lean content, breed, sex