The Effect of Supplementing Clostat 500 (Bacillus Subtilis PB6) to Yearling Steers in a Commercial Feedyard on Health, Salmonella spp. Prevalence, Feedlot Performance and Carcass Characteristics.

British and British × Continental crossbred beef steers, = 2,100; 313 ± 38 kg of initial body weight (BW) were used to evaluate the effects of supplementation to yearling steers in a commercial feedyard on health, prevalence of spp., growth performance, and carcass characteristics. Steers were blocked by arrival date and assigned randomly to pens within the block; pens were randomly assigned to 1 of 2 dietary treatments within block. Treatments, replicated in 15 pens/treatment with 70 steers/pen, included: 1) control (CON), diets containing no supplemental direct-fed microbials; 2) CLOSTAT (CLO), diets supplemented with 0.5 g/steer/d PB6 (CLOSTAT 500, Kemin Industries, Des Moines, IA) to provide 6.6 × 10 CFU/g of the active ingredient. Supplementing CLO decreased the overall incidence of morbidity ( = 0.03), 10.38% (CLO) vs. 13.43% (CON), decreased the percentage of steers treated once for bovine respiratory disease (BRD; < 0.01), 9.14% (CLO) vs. 12.76% (CON), and decreased the incidence of BRD retreatment ( = 0.03) compared with CON. Mortality did not differ among treatments ( = 0.23); however, overall deads and removals tended to be less for CLO than CON (53 heads vs. 73 heads respectively, = 0.06). Prevalence of fecal did not differ among treatments, ( ≥ 0.35); overall fecal counts tended to be less for CLO (1.59 log (10) CFU/g) than CON (2.04 log (10) CFU/g; = 0.07). concentration in subiliac lymph nodes (n =150/treatment) was not different ( = 0.62) between CON (0.22 log (10) CFU/g) or CLO (0.19 log (10) CFU/g); however, there was a 46% reduction in the overall mean prevalence of lymph node ( = 0.46; 15.48% vs. 28.66%) for CLO and CON, respectively. With deads and removals included, final BW was heavier for CLO steers than CON, (654 kg vs. 641 kg, respectively, = 0.05), and average daily gain (ADG; = 0.08) and gain efficiency (G:F; = 0.06) tended to be greater for CLO than CON. With deads and removals excluded, final BW, ADG, and G:F did not differ among treatments ( 0.30). Carcass traits were not different between treatments ( 0.15). Supplementing CLO throughout the feeding period in a commercial feedyard improved the health outcomes of yearling steers by decreasing BRD and overall treatment rates, reducing the overall abundance of , and resulting in fewer steers removed from the study compared with CON.