Effect of Direct-Fed Microbial Supplementation on Pathogenic <i>Escherichia coli</i> Fecal Shedding, Live Performance, and Carcass Characteristics in Feedlot Steers

Abstract

Three experiments were conducted to evaluate direct-fed microbial (DFM) supplementation on live performance, carcass characteristics, and fecal shedding of E. coli in feedlot steers. In Exp. 1, 400 steers (BW = 348 kg) were assigned to treatments: CON = lactose carrier only, BOV = P. freudenreichii (NP24) + L. acidophilus (NP51), BOVD = P. freudenreichii (NP24) + L. acidophilus (NP51), and COMB = BOV fed for the first 101 d on feed, followed by BOVD for the final 28 d prior to harvest. In Exp. 2 (n = 1800; BW = 354 kg) and Exp. 3 (n = 112; BW = 397 kg), steers were utilized in a randomized complete block design and assigned to DFM treatments using low dose and high dose, respectively. Fecal samples were collected prior to harvest and analyzed for E. coli serogroups. In Exp. 1, DFM reduced (P < 0.01) the concentration of E. coli O157. Prevalence of O157 was reduced by BOVD supplementation in Exp. 2 and 3 (P < 0.01 and P = 0.08, respectively), and concentration of E. coli O157 in positive samples was reduced in both experiments where enumeration was performed (P ≤ 0.02). Weighted mean differences across the three experiments were equal to a 33% reduction in the prevalence of E. coli O157:H7 in BOVD treated cattle. A significant reduction in prevalence of O26, O45, O103, and O121 was observed in Exp. 2 (P ≤ 0.03). These results indicate that high levels of L. acidophilus (NP51) may represent an effective pre-harvest food safety intervention to reduce fecal shedding of several E. coli serogroups.

Effect of a direct-fed microbial (10-G Armor) on feedlot performance, carcass characteristics, and prevalence of Salmonella in fed-beef heifers

“…Inconsistent effects of DFM supplementation on USDA quality grades have been shown with varied results. Huck et al (2000) and Thompson et al (2020) reported a similar tendency for an increased percentage of USDA Choice carcasses when fed a DFM compared with non-supplemented cattle, while other studies in which cattle were supplemented with a DFM have shown no improvement in USDA quality grade distribution ( Elam et al, 2003 ; Krehbiel et al, 2003 ; Cull et al, 2015 ). Yield grade distributions did not differ between treatment groups ( P ≥ 0.62).…”

Influence of BOVAMINE DEFEND Plus on growth performance, carcass characteristics, estimated dry matter digestibility, rumen fermentation characteristics, and immune function in finishing beef steers

“…However, other researchers have reported no impact of single bacterial strains of L. animalis or P. freudenreichii or combinations of L. animalis and P. freudenreichii , on feedlot cattle growth performance and carcass characteristics ( Vasconcelos et al., 2008 ; Luebbe et al., 2013 ; Thompson et al., 2020 ; Cull et al., 2022 ). The reason for the variable impacts of DFM supplementation on beef cattle growth and carcass characteristics is unknown.…”