The muscle, fat, and bone content of Angus steer carcasses as affected by stocking rates

Abstract

Data from the complete dissection of carcasses from a selected group of British breed cattle were used to derive regression equations for muscle, bone, and fat on the carcass variables suggested by Butteriield. These equations were used to estimate the carcass composition of 70 Angus steers which had been grazing a Phalaris tuberosa–subterranean clover pasture for 460 days. The regression equations contained data from three of these animals. Muscle was well estimated (R = 0.99) by the equation

y = 9.1009–45.0288(fat thickness, cm) + 1.0686(carcass wt., lb)

+ 0.9240(shin muscle wt., Dg).

Total bone was estimated (R = 0.99) from the equation

y (total bone, g) = –1246.55 + 16.7413(shin bone wt., g) + 4.6399(carcass wt., lb).

Fat estimation varied with the nutritional history of the animals. Total fat for animals never subjected to a lengthy stress period could be estimated (R = 0.96) from the equation

y = 75.188 + 99.352(fat thickness, cm) + 0.4499(carcass wt., lb).

The use of logarithms in the derivation of these equations generally resulted in some improvement in the multiple correlation coefficients. Values were calculated from logarithmic forms of the above equations for the muscle, fat, and bone contents of carcasses from animals which had been grazing at stocking rates of 3/8, 1/2, 5/8, 3/4 and 7/8 of a beast per acre from August 1961 to November 1962. Where the cattle had been grazing alone, both muscle and fat were significantly related to stocking rate but total bone was not. With cattle which had been grazing with sheep, only fat was significantly related to stocking rate. The use of a number of other measurements and the transformation of these variables to logarithmic form is discussed.