Investigation of feedlot-level use of a direct fed microbial on fecal shedding of E. coli O157:H7

Authors: EDACHE, DAVID - Kansas State University; BARUCH, JOAQUIN - Kansas State University; KREIKEMEIER, WANDA - Livestock Logic, Llc; NAGARAJA, TIRUVOOR - Kansas State University; RENTER, DAVID - Kansas State University; Smolensky, Dmitriy; CERNICCHIARO, NATALIA - Kansas State University

Submitted to: Journal of Food Protection
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 10/1/2024
Publication Date: N/A
Citation: N/A

Interpretive Summary: E. coli O157:H7 is a food-borne pathogen that causes gastrointestinal disease in thousands of people each year. Cattle are known to be the main source of this bacterium, and contaminated beef can pass it to humans. Several control measures, such as adding direct fed microbials (probiotic supplements) (DFM) to cattle diets, have been suggested to reduce the presence of E. coli O157 in cattle feces. While these measures have shown some benefits, the success of using commercially available DFM to reduce E. coli O157 in feedlot cattle before slaughter has been inconsistent. Our objectives were to determine if the use of a DFM (containing Lactobacillus animalis LA51 and Propionibacterium freudenreichii PF24; Bovamine Defend®) in feedlots was linked to the amount of E. coli O157 in cattle feces. We also wanted to investigate other factors that might affect E. coli O157 levels in cattle pens in Nebraska feedlots. In the summer of 2017, we sampled 20 commercial feedlots in Nebraska—ten that used DFM in the cattle diet and ten that did not. Each month, we collected fecal samples from pen floors and asked farm managers about risk factors related to E. coli O157. Samples were transported to the preharvest food safety laboratory at Kansas State University for processing and testing. Our main findings were: 1) the link between using DFM and the amount of E. coli O157 in feedlots depended on the month the samples were taken, 2) the highest levels of E. coli O157 were found in the second sampling month, from late July to mid-August, and 3) the average weight of cattle in a pen and weather conditions that were neither sunny nor cloudy were significantly linked to the amount of E. coli O157 in the pen. Although our main goal was not fully confirmed, our results suggest that using a DFM with Lactobacillus animalis LA51 and Propionibacterium freudenreichii PF26 in feedlots could help reduce E. coli O157 in cattle during peak times. Understanding how demographic and management factors, along with dietary interventions, can reduce E. coli O157 at the farm level may help improve food safety.

Technical Abstract: Our objectives were to determine whether the feedlot-level use of a direct fed microbial (DFM; Lactobacillus animalis LA51 and Propionibacterium freudenreichii PF24; Bovamine Defend®, 2x109 CFU/g) was associated with fecal prevalence and concentration of E. coli O157:H7, and determine pen- and feedlot-level risk factors associated with fecal E. coli O157:H7 prevalence in cattle pens from commercial feedlot operations. Twenty commercial feedlots in Nebraska, ten that included DFM (DFM) and ten that did not (no-DFM), were sampled during the summer of 2017. In each sampling month, 22 pen-floor fecal samples were collected from three pens in each feedlot. Samples were subjected to cultural and molecular procedures for detection of E. coli O157:H7 (immunomagnetic separation, plating on selective media, followed by PCR confirmation) and spiral plating for quantification. A total of 1,320 samples from 180 pens of finishing cattle belonging to 20 feedlots, which were sampled three times throughout a 12-week period, were processed and tested. Across all feedlots and sampling months, mean within-pen prevalence was 13.5% (95% CI = 2.6-47.4%). The association between DFM status and the within-pen prevalence of E. coli O157:H7 depended significantly (p<0.05) on the sampling month. The second sampling month between late July and mid-August, corresponded to the highest within-pen prevalence estimates reported in this study, with no-DFM pens having higher prevalence than DFM pens. After accounting for the DFM status, and based on multivariable analyses, sampling month, average pen body weight and weather conditions were significantly associated with the within-pen fecal prevalence of E. coli O157:H7. Collectively, these findings demonstrate that the use of a DFM containing Lactobacillus animalis LA51 and Propionibacterium freudenreichii PF26 in feedlots showed potential in reducing fecal E. coli O157:H7 prevalence in cattle during times when prevalence peaks.