Crude protein and amino acid requirements of growing-finishing Holstein steers gaining 1.43 kilograms per day.

Holstein steers (164 kg) were used in a 70-d growing-finishing trial. Treatments were 1) basal diet (85% concentrate); 2) basal diet plus 1.5% blood meal (BM); 3) basal diet plus 3.0% BM and 4) basal diet plus 4.5% BM. Dietary crude protein levels were 12.5, 13.7, 14.8 and 15.9% for Treatments 1 through 4, respectively. Energy intake was restricted to allow for a daily weight gain of 1.43 kg. There were no treatment effects on animal performance. The influence of protein supplementation on characteristics of ruminal and total tract digestion was evaluated in a crossover design experiment involving six ruminally and intestinally cannulated steers (191 kg). Treatments consisted of Diets 1 and 4 of the feeding trial, with chromic oxide added as a digesta marker. There were no treatment effects on ruminal or total tract digestion of organic matter. Blood meal supplementation increased (P less than .01) non-NH3-N passage to the small intestine by 27.3% and N disappearance posterior to the abomasum by 32.5%. Ruminal escape of BM was 83.2%. Extrapolating to the level of intakes achieved in the performance trial, intestinal supplies of non-NH3-N, arginine, histidine, isoleucine, leucine, lysine, methionine, phenylalanine, threonine and valine for steers consuming Treatment 1 were 119.5, 42.6, 14.7, 28.5, 49.8, 38.7, 14.1, 27.0, 28.5 and 39.0 g/d, respectively. A dietary crude protein intake of 695 g/d was adequate to meet the amino acid requirements of Holstein calves within the weight range of 163 to 267 kg and gaining 1.48 kg/d.