Influence of processing on the comparative feeding value of barley for feedlot cattle
1993
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. It is concluded that current feeding standards are accurate for DRB. However, steam processing in addition to rolling will further increase the NE(m) value of barley by 2.8 to 7.0%, depending on the thinness of the flake. Improved value of barley due to steam processing and flaking may be attributable to enhanced ruminal N efficiency, decreased ruminal methane loss, and increased total tract starch digestibility.
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