The effect of supplementing CLOSTAT 500 (Bacillus subtilis PB6) to yearling steers in a commercial feedyard on health, Salmonella spp. prevalence, feedlot growth performance and carcass characteristics

Abstract

British and British × Continental crossbred beef steers, n = 2,100; 313 ± 38 kg of initial body weight (BW) were used to evaluate the effects of Bacillus subtilis PB6 supplementation to yearling steers in a commercial feedyard on health, prevalence of Salmonella spp., growth performance, and carcass characteristics. Steers were blocked by arrival date and assigned randomly to pen within 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 Bacillus subtilis PB6 (CLOSTAT 500, Kemin Industries, Des Moines, IA) to provide 6.6 × 109 CFU/g of active ingredient. Supplementing CLO decreased the overall incidence of morbidity (P = 0.03), 10.38% (CLO) vs. 13.43% (CON), decreased the percentage of steers treated once for bovine respiratory disease (BRD; P < 0.01), 9.14% (CLO) vs. 12.76% (CON), and decreased the incidence of BRD retreatment (P = 0.03) compared with CON. Mortality did not differ among treatments (P = 0.23); however, overall deads and removals tended to be less for CLO than CON (53 head vs. 73 head respectively, P = 0.06). Prevalence of fecal Salmonella did not differ among treatments, (P ≥ 0.35); overall fecal Salmonella counts tended to be less for CLO (1.59 log (10) CFU/g) than CON (2.04 log (10) CFU/g; P = 0.07). Salmonella concentration in subiliac lymph nodes (n =150/treatment) was not different (P = 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 Salmonella (P = 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, P = 0.05), and average daily gain (ADG; P = 0.08) and gain efficiency (G:F; P = 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 (P ≥ 0.30). Carcass traits were not different between treatments (P ≥ 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 Salmonella, and resulted in fewer steers removed from the study compared with CON.

Effects of feeding CLOSTAT (Bacillus subtilis PB6) on the clinical health, performance, and carcass characteristics of feedlot steers1

“…Carcass characteristics, including HCW, dressing percentage, 12th-rib fat, longissimus muscle area, marbling score, USDA quality grade, and yield grade did not differ by treatment ( P ≥ 0.36). These results are consistent with other studies with B. subtilis PB6 supplementation to feedlot cattle ( Smock et al., 2019 ; Smith et al., 2021 ; Word et al., 2022 ). Likewise, Krehbiel et al.…”

“…Similar experiments by Smock et al. (2019) and Word et al. (2022) make no mention of incidence of toe abscesses or lameness.…”

“…(2019) reported a reduction in initial and secondary BRD treatment rates in high-risk feeder steers fed B. subtilis PB6 and a decrease in fecal Salmonella prevalence over control steers. In a commercial feedyard, supplementing B. subtilis PB6 to yearling steers reduced the overall treatment rate by 29%, lowered the initial BRD treatment rate by 39.6%, resulted in fewer cattle receiving a second BRD treatment, and fewer cattle removed from the experiment ( Word et al., 2022 ). Further, when considering the losses of dead and railer cattle in the aforementioned experiment, authors projected a 5.55:1 return on investment by feeding B. subtilis PB6.…”

“…Similarly, feedlot performance was not affected by B. subtilis PB6 supplementation to yearling steers ( Smith et al., 2021 ). Yet, supplementing B. subtilis PB6 to feedlot steers in a commercial feedyard tended to improve live cattle performance on deads and removals included basis ( Word et al., 2022 ).…”

“…The efficacy of B. subtilis PB6 in cattle has been demonstrated through previous research and has been shown to reduce the severity of salmonellosis ( Broadway et al., 2020 ), decrease BRD morbidity ( Smock et al., 2019 ; Word et al., 2022 ), and improve profitability in the feedyard ( Word et al., 2022 ). This experiment was conducted in 2017 and was the first applied study conducted with B. subtilis PB6 in feedlot cattle; therefore, the objectives of this experiment were to evaluate the effects of supplementing 13 g/steer daily of B. subtilis PB6 on the clinical health, performance, and carcass characteristics of feedlot steers.…”