The Substitution of Corn with Soybean Hulls and Subsequent Impact on Digestibility of a Forage-Based Diet Offered to Beef Cattle1

To better understand the impact of corn and soybean hull supplementation on bermudagrass hay utilization, a digestion trial was conducted using 6 ruminally cannulated steers receiving bermudagrass hay supplemented with soybean hulls (HULLS), cracked corn (CORN), or soybean hulls and cracked corn (MIX; 75% and 25%, respectively) in a 3 × 3 Latin rectangle arrangement. Total DMI was not different among treatments as measured by kilograms per day (P = 0.06; from 6.52 to 7.48 kg/d) and percentage of BW per day (P = 0.67; from 2.41 to 2.79% BW/d). Similarly, hay DMI did not differ but tended to decrease (P = 0.06) among steers receiving HULLS (2.88 kg/d; 1.08% BW/d). Apparent NDF, ADF, and hemicellulose digestibilities were greatest (P < 0.001) among steers consuming HULLS (64.92, 65.39, and 64.01%, respectively) or MIX (62.66, 63.21, and 61.78%, respectively). Total ruminal VFA production was not different (P = 0.97) among treatments (232.6 to 289.7 mM); likewise, ruminal pH did not differ (P = 0.31; 6.8 to 6.0). Acetate-to-propionate ratios did not differ (P = 0.46; 3.7 to 4.7), whereas NH3-N concentrations were greater (P = 0.05) among steers consuming HULLS and decreased for all diets 4 to 8 h post-feeding. Data seem to indicate that replacing a portion of corn with soybean hulls may successfully improve fiber digestion and improve ruminal N utilization.