Feed Intake and Digestibility by Cattle Consuming Bermudagrass or Orchardgrass Hay Supplemented with Soybean Hulls and(or) Corn

Effects of supplementing cattle con- suming 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 rf: 9.2 and 269 k 9.4 kg initial and final BW, respectively), in two simultaneous Latin squares, were given ad libitum access to bermudagrass (B ) or orchardgrass ( 0 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 supplementa- tion (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, 0, 0-C, O-H, and O-CH, respective- ly). Total tract NDF digestibility was greater (P < .05) for 0 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, 0, 0-C, O-H, and O-CH, respectively). In Exp. 2, mature cannulated beef cattle (524 k 1.6 kg BW) were used in a design similar to Exp. 1 with comparable dietary supplement levels. The concentra- tion 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.