The Evaluation of Brown Midrib Corn Silage Hybrids in Growing Diets Fed to Beef Steers

A 76-day growing study was conducted utilizing 216 crossbred steers (initial BW = 324 ± 10 kg) to evaluate the effects of three corn silage hybrids on performance when fed silage-based growing diets. The three hybrids were a standard corn silage hybrid which served as the control (CON; hybrid-TMR2R720), a bm3 bmr hybrid (BM3; hybrid-F15579S2), and an experimental bm3 bmr hybrid (BM3-EXP; hybrid-F15578XT) with floury endosperm. Silage was harvested at similar DM content, packed, and stored in concrete bunkers for approximately 5 mo until the initiation of the trial. Silages were sampled weekly and composited by month for nutrient analysis at 28 d post harvesting. Steers were limit-fed a common diet consisting of 50% alfalfa hay and 50% SweetBran^® at 2% of BW for 5 d prior to trial initiation to minimize gut fill. Following five days of limit feeding, steers were weighed for 2 consecutive days and averaged for initial BW. Cattle were stratified by BW and assigned randomly to pens with 12 steers/pen. Pens were assigned randomly to one of three treatments, with 6 replications/treatment. All diets included 15% modified distillers grains plus solubles and 5% supplement. The remainder of the diet consisted of 80% corn silage fed as 1 of the three hybrids (CON, BM3 or BM3-EXP). Ending BW was collected similar to initial BW with steers limit-fed at 2% of BW for five days and weighed for two consecutive days. Data were analyzed using the MIXED procedure of SAS with pen serving as the experimental unit. Block was included in the model as a fixed effect. The three silages had similar DM, NDF, organic acids, and pH, while the bm3 bmr silages had numerically less lignin and ADF as expected. Ending BW was greater (P < 0.01) for steers fed the BM3 and BM3-EXP compared to the CON, but not different between the two BMR varieties. Steers fed both BM3 and BM3-EXP had greater (P < 0.01) DMI and ADG compared to the steers on the CON treatment, but DMI and ADG were not different between steers in the BM3 or BM3-EXP treatments. While BM3 and BM3-EXP had greater DMI and ADG, there were no differences (P = 0.26) in G:F between the silage treatments. In silage-based growing diets, use of bm3 bmr silage increased DMI and subsequently ADG but did not affect G:F.