Evaluation of Bacillus subtilis PB6 on feedlot phase growth performance, efficiency of dietary net energy utilization, and fecal and subiliac lymph node Salmonella prevalence in spring placement yearling beef steers fed in southeastern South Dakota

Yearling crossbred beef steers [ = 238; initial shrunk body weight (BW) = 402 ± 31.2 kg] were used to investigate the influence of a probiotic on animal growth performance, efficiency of dietary net energy (NE) utilization, carcass characteristics, and fecal and subiliac lymph node prevalence during a 140-d finishing period at the Southeast Research Farm in Beresford, SD. Steers were allotted to 1 of 24 pens ( = 9-10 steers/pen) and assigned to 1 of 2 dietary treatments (12 pens/treatment): no probiotic (CON) or 0.5 g/steer/d of a PB6 probiotic (CLOSTAT500, Kemin Industries, Des Moines, IA; CLO). Bunks were managed according to a slick bunk management approach. Fecal samples were collected on study days 1, 28, 56, 112, and 140 from a subsample of steers from each pen ( = 5 steers/pen) via rectal palpation and composited by pen for the determination of prevalence using selective enrichment and culture media. Upon harvest, subiliac lymph nodes were obtained from an equal number of steers from each treatment (collected from every other steer) following evisceration and hide removal. Data were analyzed as a randomized complete block design and pen served as the experimental unit; an α of 0.05 determined significance. Live-basis final BW and average daily gain tended ( ≤ 0.06) to be reduced for CLO. No differences were detected ( ≥ 0.11) between treatments for dry matter intake or gain efficiency. Treatment neither altered the efficiency of dietary NE utilization nor calculated dietary NE content based upon observed performance ( ≥ 0.46). No differences were detected between treatments for any carcass traits ( ≥ 0.15). No was recovered in any fecal samples collected on study days 1, 28, or 56. On day 112, steers from CLO had a numerically lower ( = 0.17; 25.0 vs. 8.3%) incidence of fecal compared to CON. On study day 140, fecal incidence did not differ between treatments ( = 0.34; 0.0 vs. 8.3%) for CON and CLO, respectively. Upon harvest, no was recovered in any subiliac lymph nodes. These data indicate that PB6 did not influence feedlot phase growth performance or fecal prevalence. Additionally, was not observed in the subiliac lymph nodes of any steers upon harvest.