Young Scholar Presentation: The Effect of Corn Silage Harvest, Hybrid, and Inclusion Level on Performance in Growing and Finishing Beef Cattle.

Five experiments evaluated the effects of delayed corn silage harvest, hybrid, and inclusion level in growing and finishing diets. Experiment 1 utilized 60 crossbred steers (BW = 271 ± 32 kg) to evaluate corn silage harvested at greater DM (37 or 43%) and response to rumen undegradable protein (RUP) supplementation (0.5, 1.4, 2.4, 3.3, or 4.2% of diet DM). Experiment 2 utilized 180 crossbred yearling steers (BW = 428 ± 39 kg) to evaluate corn silage DM (37 or 43%) and replacing corn with silage (15 or 45% of diet DM). Experiment 3, utilized 360 steers (BW = 334 ± 25 kg) to evaluate corn silage hybrid and inclusion level (15 or 45% of diet DM). Silage hybrids were a standard hybrid control (CON; hybrid-TMF2R720), a bm3 brown midrib (bmr) trait (BM3; hybrid-F15579S2), and an experimental bm3 bmr hybrid (BM3-EXP; hybrid-F15578XT; Unified) with a SilaSoft kernel trait. In Exp. 4 and 5, 216 crossbred steers (BW= 324 ± 10 kg) and ruminally fistulated steers (n = 6; BW = 274 ± 27 kg), respectively, were used to evaluate silage hybrid (CON, BM3 or BM3-EXP) in growing diets. In Exp. 1 with growing cattle, as DM of silage increased from 37 to 43%, ADG and G:F were reduced (P ≤ 0.04). Increasing supplemental RUP in the diet increased (P £ 0.05) ending BW, ADG, and G:F linearly. In Exp. 2 with finishing cattle, as DM of silage increased from 37 to 43%, there were no differences (P ≥ 0.30) in DMI, ADG, or G:F. In Exp. 2 and 3, as inclusion of silage in the finishing diet increased from 15 to 45%, ADG and G:F decreased (P ≤ 0.04). In Exp 3, BMR-EXP had the greatest ADG and G:F at 15% silage. At 45% silage, both bm3 hybrids had greater (P ≤ 0.05) ADG than CON, but G:F was greatest for cattle fed BM3 (P<0.03). In Exp 4 with growing cattle, ending BW, DMI and ADG were greater (P < 0.01) for steers fed the BM3 and BM3-EXP compared to the CON. In Exp. 5, steers fed both bm3 hybrids had greater (P < 0.01) NDF and ADF digestibility than the CON. Delayed silage harvest decreased performance in growing diets, but did not affect performance of finishing cattle. Silage hybrids containing the bmr trait improved performance, and improvement was most evident with large inclusions of silage.