Influence of processing on the comparative feeding value of barley for feedlot cattle

Ninety-six crossbred steers were used in a 172-d feedlot growth performance trial to determine the effects of type processing on the comparative feeding value of barley in a 90% concentrate finishing diet. Treatments were: 1) steam-flaked corn (SFC; density = .31 kg/L); 2) dry-rolled barley (DRB; density = .39 kg/L); 3) steam-rolled barley, coarse roll (SRB-C, density = .39 kg/L); and 4) SRB, thin roll (SRB-T, density = .19 kg/L). The ADG was similar (P > .10) across barley treatments, averaging 1.29 kg/d. Feed intake (P < .05) was lower for SRB than for DRB. Diet NE was greater (P < .05) for SRB than for DRB. Feed intake was lower (P < .05) for SFC than for barley diets. The influence of grain processing on characteristics of digestion was evaluated using four Holstein steers (average BW = 230 kg) with cannulas in the rumen and proximal duodenum. Ruminal and total tract digestibility of OM and starch were lower (P < .05) for DRB than for SRB. Ruminal and total tract digestibility of OM and starch were similar (P > .10) for SRB-C and SRB-T. However, passage of nonammonia N was markedly increased (26.9%, P < .01) with SRB-T compared with SRB-C. This increase in ruminal N efficiency was due partly to reduced ruminal degradation of feed N (23.4%, P < .01) and partly to increased microbial N synthesis (13.3%, P > .10). The comparative feeding value of DRB, SRB-C, and SRB-T in this study was 90, 92, and 96% the value of SFC, respectively.(ABSTRACT TRUNCATED AT 250 WORDS)