Effects of feeding a Saccharomyces cerevisiae fermentation product compared to a direct-fed microbial in finishing diets of beef × dairy crossbred steers fed in the Pacific Northwest.

The objective of this study was to evaluate the effects of a Saccharomyces cerevisiae fermentation product (SCFP) compared to a direct-fed microbial (DFM) on growth performance, health, carcass characteristics, and liver abscess prevalence in beef × dairy crossbred steers. Two thousand steers [50% beef, 25% Holstein, 25% Jersey genetics; initial shrunk body weight (SBW) = 288.2 ± 8.0 kg] were blocked by arrival date and randomly assigned to receive 1 of 2 treatments: 1) SCFP supplied in the starter diet at 12 g per steer daily and then 9 g per steer daily in the finishing diet (NS; NaturSafe™, Diamond V, Cedar Rapids, IA) or 2) DFM fed at 50 mg per steer daily throughout the feeding period (BD; Bovamine Defend, Chr. Hansen, Milwaukee, WI). Pen served as the experimental unit (200 steers/pen), with 5 pens per treatment. Data were analyzed as a randomized complete block design in R 4.2.2. with the main effect of treatment and random effect of block included in the model. Results were reported on a deads-in basis unless otherwise stated. Cattle were fed for a total of 275 ± 6.2 d. Initial and final SBW did not differ (P ≥ 0.84) by treatment. Initial treatment pulls were observed more frequently for NS compared to BD cattle (29.43% vs. 21.67%; P < 0.01). However, NS cattle had a lesser rate of repulls as a proportion of initial pulls (10.08% vs. 16.61%; P = 0.03). Fewer (P < 0.01) bullers were reported amongst NS cattle. Cattle supplemented with NS had a lower case fatality rate (6.08% vs. 11.96%; P < 0.01) and tended to have a lower total mortality rate (1.60% vs. 2.70%; P = 0.09) than BD. With deads included, average daily gain (ADG) tended (P = 0.06) to be greater for NS cattle. Dry matter intake did not differ (P = 0.99) by treatment; however, NS cattle had a numeric advantage in feed efficiency (G:F) nearing a tendency (0.132 vs. 0.130; P = 0.11). On a deads-out basis, ADG and G:F were similar (P ≥ 0.85). Dressing percentage tended (P ≤ 0.10) to be greater for NS carcasses. Cattle fed BD had a greater (P = 0.03) proportion of USDA Prime carcasses. While treatment had no impact on liver abscess severity or total abscess occurrence, NS cattle tended to have less A- abscesses (1.72% vs. 3.87%; P = 0.10). In this large-pen comparison, SCFP supplementation improved feedlot cattle health and positively influenced performance compared to a DFM.