The Evaluation of Brown Midrib Corn Silage Hybrids and Silage Inclusion for Finishing Beef Cattle

Crossbred steers (n = 360; BW = 334 ± 25 kg) were used to evaluate three corn silage hybrids at two inclusions in finishing diets with 20% modified distillers grains with solubles. The three hybrids tested included a standard hybrid which served as the control (CON; hybrid-TMR2R720), a hybrid containing the bm3 brown midrib (bmr) trait (BM3; hybrid-F15579S2), and an experimental bm3 bmr hybrid (BM3-EXP; hybrid-F15578XT) with floury endosperm. Treatments were designed as a 2 × 3 factorial arrangement that consisted of inclusion of corn silage in the finishing diet (15% or 45% of diet DM) and silage hybrid (CON, BM3, or BM3-EXP). Steers were blocked by BW and assigned randomly within block to pen (n =36; 10 steers/pen). Data were analyzed using the MIXED procedure of SAS with pen serving as the experimental unit and block as a fixed effect. There was a silage inclusion by hybrid interaction for ADG and G:F. Cattle fed 45% silage had greater DMI (P < 0.01) compared to steers fed 15% silage. Cattle fed BM3-EXP had greater ADG than CON or BM3 when silage was included at 15% of the diet. When silage was fed at 45% of the diet DM, cattle fed BM3 and BM3-EXP gained similarly, but both were greater than CON (P < 0.05). All treatments with 15% corn silage inclusion had greater (P ≤ 0.04) G:F compared to 45% corn silage inclusion, but G:F response due to hybrid was different depending on inclusion. For steers fed 15% silage, G:F was greatest for cattle fed BM3-EXP (0.178), lowest for cattle fed BM3 (0.169), and intermediate for cattle fed CON (0.174; P < 0.05). For steers fed 45% silage, G:F was greatest for cattle fed BM3 (0.165, P < 0.03), while cattle fed CON and BM3-EXP had similar G:F (0.159 and 0.157, P = 0.24). At 15% corn silage inclusion, HCW was greater (P < 0.01) for BM3-EXP compared to CON and BM3, but similar between BM3 and CON. At 45% corn silage inclusion, steers fed BM3-EXP and BM3 had similar HCW, but were both heavier (P < 0.01) compared to CON. Cattle fed 15% corn silage had greater (P < 0.01) fat thickness and marbling score compared to steers fed 45% corn silage in the finishing diet. The response to corn hybrid varied by inclusion, but the bm3 bmr trait improved ADG and G:F depending on inclusion.