The effect of a direct-fed microbial (10-G) on live animal performance, carcass characteristics, and 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 in feces and lymph nodes. Fed beef heifers ( = 1,400; initial shrunk body weight [] 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 , , , , and ) with 10 pens per treatment. Recto-anal mucosal fecal samples (;  = 477) and subiliac lymph nodes (;  = 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 ( = 0.78), final BW ( = 0.64), average daily gain ( = 0.51), gain to feed ( = 0.71), hot carcass weight ( = 0.54), dressed carcass yield ( = 0.52), 12th rib fat depth ( = 0.13), longissimus muscle area ( = 0.62), calculated empty body fat ( = 0.26), or marbling score ( = 0.82). Distributions of liver scores ( ≥ 0.34), quality grades ( ≥ 0.23), and yield grades ( ≥ 0.11) were also not different between treatments. A tendency was detected for more normal lungs ( = 0.08; 10-G = 65.96%, CON = 61.12%) and fewer inflated lungs at harvest for cattle fed 10-G ( = 0.10; 10-G = 0.29%, CON = 1.16%); other lung outcomes did not differ ( ≥ 0.54). prevalence did not differ for RAM samples ( = 0.41; 10-G = 97.74%, CON = 96.82%) or SLN ( = 0.22; 10-G = 17.92%, CON = 13.66%). concentration of RAM samples ( = 0.25; 10-G = 3.87 log CFU/g, CON = 3.32 log CFU/g) or SLN ( = 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 carriage for heifers fed 10-G.