Investigations into the accuracy of prediction of beef carcass composition using subcutaneous fat thickness and carcass weight .2. Improving the accuracy of prediction

Attempts were made to improve the accuracy of prediction of carcass components in 68 steer carcasses using a subcutaneous fat thickness measurement (FTP8) and hot side weight as the principal or sole predictors. When carcasses were divided into two weight ranges, prediction of the percentages of carcass fat (fat %) and muscle (muscle %) in the lighter group, using FTP8, were almost as accurate (fat %: RSD, 1.83; R-2, 0.73; muscle %. RSD, 1.70; R-2, 0.47) as those given by multiple regression measurements made by advanced technologies. Prediction in the heavier weight group was unsatisfactory, featuring high RSDs and a low R-2. Because breed differences in prediction did not occur in the lighter group, a single prediction equation could be used for each carcass component. The use of fat thickness groups gave a similar result to that of weight groups. Once weight groups were used, curvilinear analysis did not improve the accuracy of prediction. In the lighter carcasses, the addition of hot side weight, eye muscle area and muscle score, singly or in combination, did not improve the accuracy of percentage predictions, In the heavier carcasses, the addition of hot side weight and eye muscle urea was necessary to give prediction of a modest level of accuracy. For the prediction of the weights of carcass components, the addition of hot side weight to FTP8 gave the most accurate prediction in light carcasses (fat weight: RSD, 1.60; R-2, 0.92; muscle weight: RSD, 2.08; R-2, 0.97). In the heavy carcasses, hot side weight and eye muscle area added to FTP8 gave the most accurate prediction (fat weight: RSD, 4.40; R-2, 0.69; muscle weight: RSD, 3.73, R-2, 0.88). Because of the high level of variance explained, it is recommended that weights of carcass components be predicted particularly in heavy carcasses. (C) 1997 Elsevier Science Ltd.