Prediction of body composition in live sheep

Abstract

New and published data on the chemical composition of 149 Merino and Merino crossbred sheep covering a wide range of age were used to derive regressions of body water, protein, ash and fat on parameters measured in the live animal. Allometric models were tested with fasted liveweight (W), tritiated water space (T) and maturity (M) as predictors, maturity being the age of the sheep as a proportion of the age at which mature size is reached. For all body components the inclusion of maturity in the following equations substantially reduced the residual standard deviation (RSD), compared with allometric or multiple linear regression models that included only W and T as predictors. In addition it largely eliminated bias from the predicted values for the six separate groups of sheep from which the data were obtained.

Total body water (kg) = 1.179T^0.926M^0.031 (RSD = &plusminus;0.354)

Protein in empty body (kg) = 0.408 W^0.708M^0.092 (RSD = &plusminus; 0.264)

Ash in empty body (kg) = 0.305 W^0.460M^0.290 (RSD = &plusminus; 0.100)

Fat in empty body (kg) = 0.117(W – T)^1.592M^-0.225 (RSD = &plusminus; 0.444)

It is suggested that in future work a measure of skeletal size in the live animal may increase the precision of these equations.