The effect of a direct-fed microbial (10-G) on live animal performance, carcass characteristics, and Salmonella prevalence of fed beef heifers.

The objective of this study was to determine the efficacy of the direct-fed microbial 10-G upon cattle growth performance, liver and lung health, carcass quality, and yield outcomes, as well as prevalence and enumeration of Salmonella in feces and lymph nodes. Fed beef heifers ( N  = 1,400; initial shrunk body weight [ BW ] 343.3 ± 36.2 kg) were blocked by the day of arrival and randomly allocated to one of two treatments (0 [negative control, CON] or 2 g of a direct-fed microbial [10-G] that provided 1 billion CFUs per animal per day of Lactobacillus acidophilus , Enterococcus faecium , Pediococcus pentosaceus , L. brevis , and L. plantarum ) with 10 pens per treatment. Recto-anal mucosal fecal samples ( RAMs ; n  = 477) and subiliac lymph nodes ( SLNs ; n  = 479) were collected longitudinally at harvest from 23 to 25 heifers per pen. Data were analyzed using mixed models; pen served as the experimental unit; block and harvest date were random effects. No differences were detected in dry matter intake ( P  = 0.78), final BW ( P  = 0.64), average daily gain ( P  = 0.51), gain to feed ( P  = 0.71), hot carcass weight ( P  = 0.54), dressed carcass yield ( P  = 0.52), 12th rib fat depth ( P  = 0.13), longissimus muscle area ( P  = 0.62), calculated empty body fat ( P  = 0.26), or marbling score ( P  = 0.82). Distributions of liver scores ( P  ≥ 0.34), quality grades ( P  ≥ 0.23), and yield grades ( P  ≥ 0.11) were also not different between treatments. A tendency was detected for more normal lungs ( P  = 0.08; 10-G = 65.96%, CON = 61.12%) and fewer inflated lungs at harvest for cattle fed 10-G ( P  = 0.10; 10-G = 0.29%, CON = 1.16%); other lung outcomes did not differ ( P  ≥ 0.54). Salmonella prevalence did not differ for RAM samples ( P  = 0.41; 10-G = 97.74%, CON = 96.82%) or SLN ( P  = 0.22; 10-G = 17.92%, CON = 13.66%). Salmonella concentration of RAM samples ( P  = 0.25; 10-G = 3.87 log CFU/g, CON = 3.32 log CFU/g) or SLN ( P  = 0.37; 10-G = 1.46 log CFU/g, CON = 1.14 log CFU/g) also did not differ between treatments at harvest. These results do not demonstrate any difference in live animal performance, carcass characteristics, or Salmonella carriage for heifers fed 10-G.