Feed intake and digestibility by cattle consuming bermudagrass or orchardgrass hay supplemented with soybean hulls and(or) corn

Effects of supplementing cattle consuming tropical or temperate grass with corn and(or) soybean hulls on feed intake and digestibility were determined. In Exp. 1, eight Holstein steer calves (210 +/- 9.2 and 269 +/- 9.4 kg initial and final BW, respectively), in two simultaneous Latin squares, were given ad libitum access to bermudagrass (B) or orchardgrass (O) hay without supplementation or with (DM basis) .5% of BW of ground corn (C), .7% of BW of soybean hulls (H), or .25% of BW of corn plus .35% of BW of soybean hulls (CH). Total OM intake was greater (P < .05) with than without supplementation (5.05, 6.04, 5.95, 6.06, 6.04, 6.81, 6.61, and 6.69 kg/d), and digestible OM intake was affected by forage source (P < .05), mixing of supplement types (CH versus the mean of C and H; P < .09), and the forage source X supplementation interaction (P < .09; 2.65, 3.40, 3.33, 3.46, 3.71, 4.14, 3.98, and 4.30 kg/d for B, B-C, B-H, B-CH, O, O-C, O-H, and O-CH, respectively). Total tract NDF digestibility was greater (P < .05) for O than for B diets and for H than for C (56.4, 53.9, 58.1, 56.9, 68.5, 64.9, 67.7, and 69.6% for B, B-C, B-H, B-CH, O, O-C, O-H, and O-CH, respectively). In Exp. 2, mature cannulated beef cattle (524 +/- 1.6 kg BW) were used in a design similar to Exp. 1 with comparable dietary supplement levels. The concentration of total VFA and acetate:propionate in ruminal fluid did not differ between C and H. Duodenal microbial N also did not differ among supplement treatments, but postruminal OM digestibility was greater (P < .06) for C than for H with both forages. In conclusion, digestible OM intake was improved similarly by supplementing growing steers consuming moderate-quality, temperate, or tropical grass hay with .5% of BW of corn or .7% of BW of soybean hulls. A mixture of corn and soybean hulls increased digestible OM intake with both forage sources relative to the mean of C and H.