An Experimental Field Trial Investigating the Use of Bacteriophage and Manure Slurry Applications in Beef Cattle Feedlot Pens for Salmonella Mitigation

Abstract

Post-harvest Salmonella mitigation techniques are insufficient at addressing Salmonella harbored in cattle lymph nodes, necessitating the exploration of pre-harvest alternatives that reduce Salmonella prior to dissemination to the lymph nodes. A 2 × 2, unbalanced experiment was conducted to determine the effectiveness of pre-harvest treatments applied to the pen surface for Salmonella mitigation in cattle. Treatments included manure slurry intended to mimic pen run-off water (n = 4 pens), a bacteriophage cocktail (n = 4), a combination of both treatments (n = 5), and a control group (n = 5) that received no treatment. Environment samples from 18 feedlot pens and fecal grabs, hide swabs, and subiliac lymph nodes from 178 cattle were collected and selectively enriched for Salmonella, and Salmonella isolates were sequenced. The combination treatment was most effective at reducing Salmonella, and the prevalence was significantly lower compared with the control group for rump swabs on Days 14 and 21. The treatment impact on Salmonella in the lymph nodes could not be determined due to low prevalence. The reduction on cattle hides suggests that bacteriophage or water treatments applied to the feedlot pen surface may reduce Salmonella populations in cattle during the pre-harvest period, resulting in reduced contamination during slaughter and processing.