Effect of bambermycin and dietary distillers grains concentration on growth performance and carcass characteristics of finishing steers

An experiment was conducted comparing medicated feed additives (MFA) bambermycin or monensin sodium and tylosin phosphate in feedlot diets containing modified distillers grains (mDGS). Crossbred steers (n = 256; initial full BW 418 ± 28.5 kg) were allocated into three weight blocks in a randomized complete block design with a 2 × 2 factorial arrangement of treatments. The factors were: MFA (bambermycin at 20 mg/steer daily or monensin + tylosin at 380 and 90 mg/steer daily, respectively) and mDGS inclusion (15% and 30% of diet DM). Twenty-four pens were utilized, resulting in six replications per treatment. Steers were fed a diet consisting of a 1:1 combination of dry-rolled and high-moisture corn with the roughage portion of the diet consisting of corn silage and corn stover. Steers in the heaviest two blocks were marketed after 104 d and steers in the lightest block were marketed after 126 d. Overall average daily gain (ADG) tended (P = 0.08) to be greater for bambermycin vs. monensin and tylosin, and was not affected (P = 0.17) by mDGS level. Dry matter intake was lower (P ≤ 0.05) with 30% mDGS with monensin and tylosin than with any other treatment. Feed efficiency was not affected by mDGS, MFA, or their interaction (P ≥ 0.30). Marbling scores were greater (P = 0.01) greater for bambermycin vs. monensin and tylosin, and tended (P = 0.08) to be greater with 15% mDGS than with 30% mDGS. Carcasses from steers fed bambermycin had a greater percentage of USDA choice than those fed with monensin and tylosin (P = 0.01). Liver abscess occurrence was not affected (P ≥ 0.17) by MFA, mDGS, or their interaction. Results from this experiment indicate that including bambermycin in feedlot diets containing 30% mDGS results in increased DMI when compared with including monensin and tylosin in 30% mDGS diet without the risk for increases in liver abscess occurrence.