Prevalence of Microbial Threats in Dairy Production According to the Cattle Feeding System

Introduction: Interventions aimed upstream of the food chain can help to reduce at the source microbial contaminants associated with foodborne diseases such as non-typhoidal Salmonella, enteropathogenic Escherichia coli and Listeria monocytogenes. These microorganisms are recognized as the main causative agents of gastroenteritis in Canada. In fact, farm characteristics and management practices can affect the abundance of bacterial pathogens in a given herd. The component-fed rations (CFR) feeding system could represent a potential risk factor for an increased prevalence of foodborne pathogens, as it is frequently distributed manually by the producer, compared to a total mixed rations (TMR) feeding system, which is often distributed automatically.

Purpose: To determine whether the use of CFR systems, compared to TMR systems, can influence the prevalence of three foodborne microorganisms in animals from dairy herds.

Methods: Ten similar dairy cattle farms using a CFR system (n=5) or a TMR system (n=5) were each visited four times over a one-year period. Rectal samples (50 g) were collected from 15 lactating cows per farm per visit for a total of 600 samples. Using the appropriate selective media, Salmonella spp., E. coli O157:H7, and L. monocytogenes were isolated from the feces collected. Confirmatory bacterial identification was performed by PCR on isolated colonies.

Results: The prevalence of Salmonella spp., L. monocytogenes, and E. coli O157:H7 in CFR-fed animals (n=300) were 5.7%, 7.7%, and 1.7%, respectively, compared to 1.3%, 8.3%, and 0% in TMR-fed animals (n=300). The difference was statistically significant for Salmonella (P=0.004) and for E. coli (P= 0.025). The peak in detection occurred during spring for all pathogens.

Significance: In this study, the CFR feeding system is associated with a higher prevalence of certain microorganisms. Characterizing production practices is still necessary in order to implement effective control strategies for bacteria that can affect food safety.