Influence of commercial yeast products in diets for beef cattle new to the feedlot environment

ABSTRACT Objective Bovine respiratory disease is of great concern for stocker producers in the southeastern United States. Thus, this research was conducted to test the effects of yeast products on health and performance of high-risk, newly received beef calves. Materials and Methods Male beef calves (n = 175; initial BW = 226 ± 24.5 kg) were delivered in 2 arrival blocks (arrival block 1: n = 85 with 54 bulls and 31 steers; arrival block 2: n = 90 with 62 bulls and 28 steers). Within arrival block, calves were blocked by initial BW, stratified by castrate status, and assigned randomly to pen (5 or 6 calves per pen; 15 pens per truckload). Pens within each weight block were allocated to 1 of 3 treatments: unsupplemented control or supplementation with either brewers yeast or yeast culture for 28 d. 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 feed bunks immediately after basal diet delivery. Results and Discussion Average daily gain from d 0 to 28 was not different (P = 0.99) between treatments. Providing yeast product did not affect ADFI (P ≥ 0.92) or G:F (P ≥ 0.91). Percentage morbidity (P = 0.36), percentage of bovine respiratory disease relapses (P = 0.32), and days to first antibiotic treatment (P = 0.17) did not differ. Application In high-risk calves with over 50% morbidity by d 5, neither of the yeast products provided during this trial influenced health and growth performance.