Quantitative estimates of lamb carcass composition 2. Specific gravity determination

Abstract

SUMMARYRelationships between specific gravity and carcass tissue were studied in 83 purebred Clun Forest lambs slaughtered at approximately 80 lb. liveweight and ranging in carcass weight from 29 to 42 lb. Carcass specific gravity accounted for 86·1% and 78·1% of the respective variances in carcass fat percentage and muscle percentage. Specific gravity determinations on a single joint were also highly correlated with the carcass tissues. Correlation coefficients between loin specific gravity and carcass fat and muscle were −0·89 and 0·82 respectively; corresponding figures for best-neck specific gravity were −0·86 with carcass fat percentage, and 0·76 with carcass muscle percentage. In partial correlation analyses, muscle/bone ratio failed to have a significant effect on these relationships. The usefulness of estimates of carcass composition based on specific gravity determinations is discussed in relation to the maximum probable errors associated with predicted values and with reference to the accuracy of these estimates under different experimental conditions. The magnitude of the confidence limits (P = 0·05) on individual predictions varied from ±2·98% to ±3·48% for fat and muscle respectively and for group (n= 12) predictions, from ±0·88% to ±1·01% respectively. This suggests that little confidence can be placed in specific gravity determinations as a reflection of real individual differences or small treatment differences.