75. Effects of Different Feed Additives on Intake, Growth Performance, and Carcass Characteristics of Finishing Beef Cattle

Abstract Improving feed efficiency in finishing beef cattle is essential for maximizing feedlot profitability. Ruminal fermentation characteristics and dry matter (DM) intake (DMI) in feedlot cattle can be influenced by feed additives, which ultimately impact feed efficiency. Although monensin is the main additive used to enhance feed efficiency in feedlot diets, the variation in composition and action of commercially available plant-based additives requires further investigation to determine their combined impact on finishing beef cattle growth performance. Therefore, the objective of this study was to evaluate the effects of feed additives on intake, growth performance, and carcass characteristics of finishing feedlot cattle. A total of fifty-six (n = 56) steers [British × Continental crossbreed; initial body weight (BW) = 356 ± 26.4 kg] were used in a randomized complete block design to evaluate four treatments: Control (CON): no feed additive in the basal finishing diet; Monensin (MON): dietary supplementation of sodium monensin at 33 mg/kg of dry matter (Rumensin 90, Elanco Animal Health); CattIActive (CA): dietary supplementation with CattIActive (a proprietary multi-component feed additive containing orange peel bitters, onion extract, specific fatty acids, and soybean and corn oil; Pro Earth Animal Health) at 10 g/head/day; and Monensin + CattlActive (MON+CA): combination of sodium monensin (33 mg/kg of dry matter) + CattIActive (10 g/head/day). Feed additives were incorporated into the mineral and vitamin supplement included at 5% of the dietary DM. The basal finishing diet contained 10% roughage and 90% concentrate. Steers were adapted to the finishing diet during the first 24 days using three step-up diets. The feeding period lasted 168 days. Data were analyzed using the MIXED procedure of SAS. Treatments did not affect body weight at the end of the adaptation period (P ≥ 0.27) or at the end of the experiment (P ≥ 0.77). No effect of treatments was observed on DMI during either the adaptation or total feeding period (P ≥ 0.26). Steers fed CA gained more weight than MON (P = 0.05) during the adaptation period, but no differences were observed between CA, CON, or MON+CA (P ≥ 0.11). Consequently, feed efficiency was greater for steers fed MON+CA compared with CON and MON (P ≤ 0.03) but not compared to CA (P = 0.40) during the first 24 days on feed. No treatment effects were detected for feed efficiency at the end of the experiment (P ≥ 0.58). Treatments did not affect the final body weight (P ≥ 0.66) or carcass characteristics (P ≥ 0.12). In summary, feeding CA or MON+CA enhanced feed efficiency during the adaptation to high-concentrate diets, but no major differences in growth performance and carcass characteristics were observed among feed additives at the end of the experiment.