Effects of Supplement Strategy on Intake and Digestion of Prairie Hay by Beef Steers and Plasma Amino Acid Concentrations

Twelve steers (373 kg initial BW) were used in three simultaneous 4 × 3 incomplete Latin squares to evaluate the effects of supplemental corn (1.8 kg/d, 0.14 kg CP/d), cooked molasses block (0.45 kg/d, 0.14 kg CP/d), and rumen-protected methionine (RPM; 3.5 g DL-methionine/d) on intake and digestion of prairie hay (5.7% CP, 72.3% NDF on DM basis). Steers that consumed the cooked molasses block ate more (P<0.05) forage OM (7.0 kg/d) and those fed supplemental corn ate less (P<0.05) forage OM (5.5 kg/d) than control steers (6.2 kg/d). Total OM intake was higher (P<0.05) for steers consuming the corn (7.0 kg/d) and cooked molasses block (7.3 kg/d) than for control animals (6.2 kg/d). Digestible OM intake was lower (P<0.05) for steers assigned to the control treatment (3.1 kg/d) than for steers consuming the cooked molasses block (3.9 kg/d) or corn (3.6 kg/d). Digestible NDF intake was higher (P<0.05) for steers assigned to the molasses block treatment (2.9 kg/d) and lower (P<0.05) for steers assigned to supplemental corn (2.0 kg/d) than for those steers assigned to the control treatment (2.4 kg/d). Although RPM increased plasma methionine concentrations (P<0.05), it was ineffective in stimulating forage intake or digestion. In summary, supplementation with a cooked molasses block increased digestible OM intake by increasing forage intake and digestion, whereas corn supplementation depressed forage intake but nonetheless increased total digestible OM intake.