Supplementing a yeast-derived product to feedlot cattle consuming monensin: Impacts on performance, physiological responses, and carcass characteristics

Feed additives are included into finishing diets to improve cattle growth and feed efficiency, resulting in enhanced productivity and profitability in feedlot systems. Yeast-derived products and monensin have analogous and complementary benefits to rumen function and cattle production. Hence, this experiment evaluated the impacts of supplementing a yeast-derived product (Celmanax; Church & Dwight Co., Inc.; Princeton, NJ, USA) during the finishing period on performance, physiological responses, and carcass quality of feedlot cattle consuming monensin. Eighty-nine Angus steers (13 months of age) were housed in a feeding facility 15 days prior to the beginning of the experiment, which was equipped with Calan gates for individual feed delivery. Steer BW was collected on days -3, -2, and -1, averaged, and represented steer initial BW (446 +/- 5 kg of BW). On day 0, steers were ranked by initial BW to receive a finishing diet containing (CEL) or not (CON) 16 g/steer daily (asfed basis) of the yeast-derived product. The finishing diet was a total-mixed ration (TMR) including (DM basis) 22% corn silage, 70.2% ground corn, 5% soybean meal, 1.8% mineral and vitamin mix, and 1% urea. Monensin was included in the TMR at 30 mg/kg of DM. The yeast-derived product was mixed with 100 g of soybean meal and top-dressed daily into the TMR of CEL steers, whereas 100 g of soybean meal was top-dressed daily into the TMR of CON cohorts. Steers received TMR and treatments until slaughter, after 132.5 +/- 1.2 days on feed. Intake of the TMR was recorded daily from day -15 until slaughter. Steer BW was also recorded for 3 consecutive days prior to slaughter, and averaged for final BW. Feed efficiency was calculated from each steer according to TMR intake and BW gain during the experiment. Blood samples were collected on days 0, 64, and the day prior to slaughter, and analyzed for plasma glucose, haptoglobin, insulin, leptin, and insulin-like growth factor (IGF)-I. Carcass parameters were recorded upon slaughter. No treatment effects were detected (P >= 0.25) for BW gain, TMR intake, feed efficiency, and carcass quality traits. No treatment effects were also detected (P >= 0.39) for plasma concentrations of glucose, insulin, leptin, and IGF-I, whereas mean plasma haptoglobin concentrations tended (P = 0.09) to be less in CON vs. CEL steers. Collectively, including a yeast-derived product into a finishing diet containing monensin did not improve performance, physiological responses, and carcass quality of feedlot cattle.