Quantitative estimates of lamb carcass composition 3. Carcass measurements and a comparison of the predictive efficiency of sample joint composition, carcass specific gravity determinations and carcass measurements

Abstract

SUMMARYInterrelationships between carcass measurements were studied in 83 purebred Clun Forest lambs slaughtered at approximately 80 lb. live-weight and ranging in carcass weight from 29 to 42 lb. Individual carcass measurements did not have a worthwhile predictive value; apart from loin (C) and rib (J) fat depths none of 12 external or internal carcass measurements showed a correlation with carcass composition greater than r = 0·70. Similarly, none of 9 offal measurements recorded had a worthwhile predictive value. In multiple regression certain combinations of these measurements accounted for as much as 77% of the variation in carcass fat, 64% in carcass muscle and 64 % in carcass bone.The predictive efficiency of sample joint composition, specific gravity determinations and carcass measurements were evaluated in terms of the increased error variance using predicted values and the effect of this increase on sample size in treatment comparisons. Generally the results indicated that increasing treatment group size by relatively few animals is sufficient to absorb the additional error variance arising from the use of predicted values. This is particularly true where treatment differences of the order of one standard deviation exist and where part-carcass dissection values are used.