New approaches to corn silage use in beef cattle finishing diets

Two finishing and one digestibility experiments evaluated the partial substitution of corn with corn silage (CS) and corn modified distillers grains with solubles (MDGS). Steers were used in Exp. 1 (n = 295; 467 ± 52 kg) and Exp. 2 (n = 225; BW = 348 ± 27 kg) in a 2 x 2 + 1 factorial arrangement of treatments with factors including CS (15 or 45%) and MDGS (20 or 40%) (15:20 – 15% CS, 20% MDGS; 15:40 – 15% CS, 40% MDGS; 45:20 – 45% CS, 20% MDGS; 45:40 – 45% CS, 40% MDGS) plus a control diet consisting of 5% cornstalks and 40% MDGS. In Exp. 1, there were tendencies for a CS X MDGS interaction for ADG, final BW, and G:F (P ≤ 0.08). In the overall F-test for G:F, there were no differences between the control treatment and 15:20, 15:40, or 45:40 (P ≥ 0.15), however, steers fed the control treatment had increased G:F compared to steers fed 45:20 treatment diets (P = 0.03). In Exp. 2, there were no CS x MDGS interactions (P ≥ 0.12). As CS increased in the diet, ADG, final BW, and G:F decreased (P ≤ 0.01). As MDGS increased from 20 to 40%, ADG and G:F tended to improve (P ≤ 0.07). In the overall F-test, the control was not different for G:F from 15:20, 45:20, or 45:40 (P ≥ 0.15), but had a 4.8% poorer G:F compared to 15:40 (P < 0.01). In Exp. 3, ruminally fistulated steers (n = 6) were used in a 5 x 6 Latin rectangle design 15 or 45% CS and 20 or 40% MDGS as a 2 X 2 factorial in addition to a +1 consisting of 95% CS and 5% supplement. There were no CS x MDGS interactions for nutrient intake, total tract digestibility, ruminal pH measurements, acetate: propionate ratio (A:P), or in-situ disappearance data (P ≥ 0.31) for the 2 X 2 factorial. As CS increased in the diet, DMI, NDF intake, ruminal pH, A:P, in-situ NDF disappearance of corn bran, and DM disappearance of corn increased (P ≤ 0.09) with decreases in DM and OM digestibility (P