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 E. coli O157. Prevalence of O157 was reduced by BOVD supplementation in Exp. 2 and 3 (P 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.
Highlights
The United States Center for Disease Control (CDC) estimates that 48 million Americans are affected by foodborne illness each year, and E. coli O157:H7 alone causes more than 70,000 illnesses and 61 deaths [1]
No significant differences or tendencies were observed for any feedlot performance parameters or carcass characteristics measured in this study (Table 2 and Table 3, respectively)
E. coli O157:H7 enumeration of positive samples resulted in a reduction of 2.13 log10 cycles (P < 0.01) when cattle were supplemented with BOVD versus CON
Summary
The United States Center for Disease Control (CDC) estimates that 48 million Americans are affected by foodborne illness each year, and E. coli O157:H7 alone causes more than 70,000 illnesses and 61 deaths [1]. This and other Shiga toxin-producing E. coli (STEC) have been linked to numerous incidents [2]. The USDA has suggested that, in addition to current HACCP plans, harvest facilities should source and receive cattle from producers who implement pre-harvest interventions to reduce shedding of these pathogens [7]
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