Effects of feeding 10-G direct-fed microbial on feedlot performance, carcass characteristics, and prevalence of Salmonella in subiliac lymph nodes of feedlot steers.

Yearling crossbred beef steers [n = 6,400; initial body weight (BW) 358 kg] were used to investigate the efficacy of a direct-fed microbial upon animal growTh performance, carcass characteristics, and prevalence of Salmonella in subiliac lymph nodes after a feeding duration of 182 d. Steers were allocated to 1 of 32 pens [n = 200/pen] within 16 total blocks, and assigned to 1 of 2 dietary treatments; no probiotic (CON) or 2 g*steer^-1*d^-1 of Lactobacillus acidophilus, Enterococcus faecium, Pediococcus pentosaceus, Lactobacillus brevis and Lactobacillus plantarum providing a total of 1 billion CFU (10-G). At harvest, subiliac lymph nodes were randomly obtained from 40 animals from each pen for blocks 1 through 10. Data were analyzed as a randomized complete block design, and pen served as the experimental unit. No differences (P ≥ 0.26) were observed between treatments for DMI, final BW, average daily gain, or feed efficiency. When evaluating carcass characteristics, there were no differences (P ≥ 0.15) for hot carcass weight or liver abscess prevalence. However, dressed carcass yield differed (P = 0.02) between treatments (CON = 64.74%, 10-G = 64.52%). No differences (P ≥ 0.12) were observed for marbling score, longissimus muscle area, 12^th rib s.c. fat depth, or USDA quality grade outcomes. Lower frequency (P < 0.01; CON = 36.95%, 10-G = 23.60%) of Salmonella positive subiliac lymph nodes was observed for cattle supplemented dietary 10-G, whereas concentration of Salmonella quantifiable samples did not differ (P = 0.23) between treatments (CON = 0.84 Log₁₀CFU/g, 10-G = 0.63 Log₁₀CFU/g). In conclusion, the supplementation of 10-G direct fed microbial did not influence live or carcass performance within this trial; however, prevalence of Salmonella positive subiliac lymph nodes was reduced.