Influence of Commercial Yeast Products in Diets for Beef Cattle New to the Feedlot Environment

Two truckloads of male beef calves (n = 172; initial BW = 226 ± 24.5 kg) were purchased from regional livestock markets to evaluate the effect of commercial yeast products on health and growth performance during a 28-d receiving period. Within truckload, calves were blocked by initial BW, stratified by gender, and assigned randomly to pen (5 or 6 calves/pen; 15 pens/truckload). Pens within each weight block were allocated to 1 of 3 treatments; an unsupplemented control, or supplementation with 2 commercial Saccharomyces cerevisiae yeast products (Y1 or Y2) resulting in 10 pens/treatment. Each day, a mixture (0.14 kg/d for each calf) of 58% ground corn and 42% of the appropriate yeast product, or 100% ground corn (control) was added to the feedbunks immediately after basal diet delivery and hand mixed into the feed offered. The basal diet contained 40% corn, 20% cottonseed hulls, 19% dried distiller grains, 10% corn gluten meal, and 7% soybean meal. Data were analyzed using the MIXED and GLIMMIX procedures of SAS with an alpha of 0.05 for all dependent variables. Final BW at the end of the 28-d trial were 255, 255, and 254 kg (P = 0.99) for the control, Y1, and Y2 treatments, respectively. Average daily gain from d 0 to 28 was not different (P = 0.99) between control, Y1, and Y2. Supplementation did not affect DMI (P ≥ 0.92) or gain:feed ratio (P ≥ 0.91). Morbidity was observed daily at feeding. Percentage morbidity due to bovine respiratory disease (BRD) was not altered (P = 0.29) with control, Y1, or Y2 (64.5%, 76.7%, and 63.0%), respectively. The percentage of relapses were 32.7, 38.8, and 51.9 (P = 0.36) for the control, Y1, and Y2, respectively. Days until first antibiotic treatment were not different (P = 0.17) between the 3 treatments. Antibiotic treatments began on d 2 and by d 5 approximately 50% of calves had been administered their first antibiotic. Antibiotic treatment costs were not different (P = 0.78) for control, Y1, and Y2. Given that the cost of antibiotic treatment was not different between groups, the addition of yeast did not provide an economic benefit in prevention against BRD. In high risk calves with over 50% morbidity by d 5, providing yeast products did not have an effect on health and growth performance.