Figure 2.

Effect of yeast supplementation on serum cortisol response in beef heifers (n = 16/trt). Heifers were fed one of two dietary treatments: 1) negative control (CON), fed a standard feedlot diet, or 2) the same standard feedlot diet with 2.5 g·heifer⁻¹·d⁻¹ live yeast and 2.5 g·heifer⁻¹·d⁻¹ yeast cell wall product (Phileo Lesaffre Animal Care, Milwaukee, WI) for 31 d prior to challenge (YST). All heifers were challenged intranasally with 2 × 10⁸ plaque-forming units bovine herpesvirus-1 at −144 h and 3 × 10⁷ colony-forming units Mannheimia haemolytica at 0 h. Data presented as least squares means ± SEM. There was no treatment × time interaction (P = 0.98) and serum cortisol was not affected by dietary treatment (P = 0.90), although serum cortisol decreased over time (P < 0.01) as cattle adapted to stanchions.