CARCASS COMPOSITION OF STEERS GIVEN HAY, HAY SUPPLEMENTED WITH RUMINAL UNDEGRADABLE PROTEIN, OR CONCENTRATE

Abstract

Holstein steers (10 per group) were given either 85% grass hay and 15% concentrate (group 1), the same diet with added rumen undegradable protein to raise the overall protein level from 120 to 130 g kg−1 (group 2), or 85% concentrate and 15% grass hay (group 3) until they were slaughtered at 500 kg. Extractable fat in separable muscle was greatest for steers in group 3, least for steers in group 2, and intermediate for those in group 1. Loin-eye area was less for steers in groups 1 and 2 than for those in group 3. Carcasses were a larger proportion of empty liveweight in steers in group 3 than in those in groups 1 and 2 due primarily to increased adipose tissue in the front quarter. In comparison with steers on a mainly hay diet, a hay diet supplemented with rumen undegradable protein did not affect the composition of the carcass although it increased the rate of gain from weaning to slaughter. Key words: Carcass, composition, nondegradable, protein, steer