Effects of feeding generic ractopamine (Actogain) with or without the combination of monensin and tylosin phosphate on growth performance, carcass characteristics, and tenderness of finishing steers

The objectives of this study were to evaluate the effects of generic ractopamine (Actogain) with or without the combination of monensin and tylosin on growth performance, carcass characteristics, and tenderness of finishing steers. A total of 1,230 steers were finished in 6 blocks based on allocated BW, where each block had 3 pens (1 pen per treatment). Steers were assigned to 1 of 3 different finishing diets for the final 33 or 34 d before slaughter: (1) no generic ractopamine with monensin and tylosin (CON + M/T), (2) generic ractopamine without monensin and tylosin (ACTO − M/T), or (3) generic ractopamine with monensin and tylosin (ACTO + M/T). Steers fed ACTO − M/T and ACTO + M/T had greater (P < 0.0001) final BW, ADG, G:F, and HCW compared with steers fed CON + M/T. Interestingly, steers fed ACTO − M/T had 5-kg-greater (P < 0.01) final BW than steers fed ACTO + M/T. However, DMI was 1.06 and 1.00 kg greater (P < 0.0001) in steers fed ACTO − M/T compared with steers fed ACTO + M/T and CON + M/T, respectively. Marbling scores were 20.3 units less (P = 0.01) in steers fed ACTO + M/T compared with steers fed CON + M/T. There were no treatment differences (P ≥ 0.06) for YG parameters (excluding HCW), calculated YG, or Warner-Bratzler shear force. In conclusion, final BW, ADG, G:F, and HCW were increased in steers fed ACTO with or without M/T compared with steers fed CON + M/T, and other carcass characteristics were minimally affected among treatments.