Effect of Feeding Brown Midrib Corn Silage in Growing Diets for Beef Cattle on Nutrient Digestibility and Ruminal Fermentation Characteristics

Feeding corn silage in combination with distillers grains has been shown as a potentially efficient way to grow steers prior to finishing. Our objective was to evaluate the effects of different silage hybrids on nutrient digestibility for growing beef cattle. Six ruminally fistulated steers (BW = 274 ± 27 kg) were utilized in a 126-d metabolism study with a replicated, 3 × 6 Latin rectangle experimental design. Three dietary treatments utilizing three different silage hybrids were compared. The three hybrids were a standard corn silage hybrid which served as the control (CON; hybrid-TMR2R720), a bm3 brown midrib (bmr) hybrid (BM3; hybrid-F15579S2), and an experimental bm3 bmr hybrid (BM3-EXP; hybrid-F15578XT) with a floury endosperm. All diets included 15% modified distillers grains plus solubles and 5% supplement. The remainder of the diet consisted of 80% corn silage of 1 of the three hybrids (CON, BM3 or BM3-EXP). Period length was 21 d which consisted of 16 d adaptation and 5 d fecal collection. Titanium dioxide was dosed intraruminally on d 10 to 20 as a marker to determine digestibility. Ruminal pH was continuously monitored with indwelling pH probes during each collection period. Corn bran and each silage were incubated for 30 h on d 21 to evaluate in situ NDF disappearance. Data were analyzed as a replicated Latin rectangle with steer as the experimental unit. Corn silage treatment tended (P = 0.11) to impact DMI and OM intake, with steers fed BM3 and BM3-EXP having greater intake than CON steers. Digestibility of OM was impacted by treatment (P = 0.06), with steers fed BM3-EXP (72.4%) having greater (P < 0.05) OM digestibility than steers fed CON (67.7%) and steers fed BM3 being intermediate but not different (P > 0.11) from steers fed either BM3-EXP or CON. Steers fed both BM3 (58.4%) and BM3-EXP (58.2%) had greater (P < 0.01) NDF digestibility than the CON (46.5%). Similarly, there were no differences (P = 0.29) in ADF digestibility between BM3 (58.1%) and BM3-EXP (53.3%), but both were greater (P < 0.01) in ADF digestibility than CON (40.8%). Average ruminal pH for steers fed bm3 bmr hybrids (6.24) was lower (P < 0.01) compared to CON (6.50). In situ NDF disappearance was greater (P < 0.01) for samples incubated in steers fed bm3 bmr hybrids compared to samples incubated in steers fed CON. In silage-based growing diets, use of bm3 bmr silage increases fiber digestibility.