158. Evaluation of Feed Additives Combinations with Monensin on Performance of Finishing Beef Cattle.

Abstract

Strategies combining multiple feed additives have been explored to enhance performance and feed efficiency in finishing beef cattle. Therefore, a large-pen trial was conducted to evaluate the effects of combining monensin, essential oils, yeast culture, and chromium supplementation on performance and dry matter intake (DMI) dynamics. A total of 2,640 24-month-old Nellore bulls [371.85 ± 32.8 kg body weight (BW); mean ± SD] were assigned to 48 open dry-lot pens (n = 55 animals/pen; 16 pens/treatment) in a randomized complete block design (8 blocks based on initial BW), with ad libitum access to feed and water. Treatments consisted of three feeding additive strategies: 1) MON: monensin at 25 mg/kg of DM; 2) MON + EO: monensin at 25 mg/kg of DM + essential oils at 20 mg/kg of DM containing 43% cinnamaldehyde and 7% garlic oil; 3) MON + EO + YE + Cr: monensin at 25 mg/kg of DM + essential oils at 10 mg/kg of DM containing 20% capsicum + yeast culture at 0.7 g/kg of DM + chromium propionate at 0.4 mg/kg of DM. Diets were formulated to meet nutrient requirements for an average daily gain (ADG) of at least 1.5 kg according to the LRNS model. Dry matter intake curves were evaluated at the pen level for each treatment using generalized additive mixed models (GAMMs). Carcass traits were analyzed considering pen as the experimental unit using SAS version 9.4 (SAS Institute Inc.). No differences were detected in final body weight (FBW) or average daily gain (ADG) among treatments (P > 0.05; Table 1). Average DMI was also not different among treatments when expressed either in kg/day or as a percentage of BW (P = 0.913 and P = 0.906, respectively). Differences were detected only during the adaptation phase (P = 0.011). The MON treatment resulted in lower DMI (9.98 kg) compared with MON + EO (10.11 kg) and MON + EO + YE + Cr (10.03 kg). Additionally, when DMI was evaluated over time (Figure 1), differences among feeding additive strategies were observed during specific periods (P < 0.05), with lower DMI for MON compared with MON + EO during the first 21 days of the feeding period. No differences in DMI dynamics were observed between MON vs. MON + EO + YE + Cr or MON + EO vs. MON + EO + YE + Cr. Carcass performance was not affected by treatments (P > 0.05). In conclusion, considering both performance and intake responses, all feeding additive strategies resulted in similar outcomes in finishing Nellore bulls.

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