Evaluation of Commercially Manufactured Animal Feeds to Determine Presence of Salmonella, E. coli and Clostridium perfringens

Animal feed can potentially expose animals to pathogens which may lead to infection or colonization of the gastrointestinal tract. Feeds can become contaminated with bacterial pathogens during harvesting and transportation of the ingredients, processing at the feed mill, transportation to the farm or during storage. These bacteria have the potential to colonize the animal leading to disease of the animal and during processing may lead to contamination of the carcasses with foodborne pathogens. The objective of the study was to establish if commercially manufactured animal feed serves as a source of contamination of Salmonella, E. coli and Clostridium perfringens. Four commercial feed mills and the research feed mill at Auburn University were sampled. A total of 140 samples (60 of ingredients and 80 of feeds) were collected from 5 different locations within each feed mill: ingredient receiving, post mixing, post pelleting (hot sample), post cooling the pellets and at loadout. All samples were assayed for Salmonella, E. coli and Clostridium perfringens using selective media. Resulting counts were log10 transformed and then analyzed using ANOVA, if significant (P<0.05), means were separated using Tukey HSD. The data shows that Clostridium spp. load in corn meal varied between the 5 feed mills (0.90 – 3.63). Feed mill A (0.90) and feed mills B, C and E (3.48, 3.48 and 3.63, respectively) were determined to be significantly different. For soybean meal, feed mill A showed the highest E. coli (3.00) counts, being significantly higher compared to the rest of the feed mills (B-E). From the processed samples, post mixing showed significance in E. coli values between feed mills C and B, with feed mill B having log10 4.84 CFU/g. In addition from processed feed Clostridium perfringens was isolated and confirmed via PCR from two samples from two different feed mills. No recontamination of E. coli was observed after pelleting the animal feeds and no Salmonella contamination was detected in ingredients or processed feed throughout the study. For future research, greater attention should be placed on Clostridium perfringens contaminated animal feed as a possible source of disease transmission to the birds.