Submitted to: Poultry Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 10/27/2011
Publication Date: 5/1/2012
Citation: Jones, D.R., Anderson, K.E., Guard, J.Y. 2012. Prevalence of coliforms, Salmonella, Listeria, and Campylobacter associated with eggs and the environment of conventional cage and free range egg production. Poultry Science. 91:1195-1202.
Interpretive Summary: US consumers are becoming more aware of the agricultural practices utilized in the production of food. As such, some consumers are requesting products, such as eggs, from alternative production systems. While agricultural industries are making shifts to provide alternatively produced items for consumers, the effects of alternative production systems on food safety are not completely understood. A study comparing environmental and egg microbiology for conventional cage and free range sister flocks of laying hens was conducted. Sampling occurred throughout the entire life cycle of the flocks. A greater prevalence of Campylobacter was found in the free range production than conventional cage environments. While Listeria was detected, there were no differences amongst the treatment for prevalence. There were no differences in Salmonella prevalence amongst treatments either. All treatments tested positive for Salmonella during the study. Additional research is needed to gain a full understanding of the food safety implications of alternative egg production systems.
Technical Abstract: There is a desired by US consumers for eggs produced by hens in alternative production systems. As the retail shell egg market offers these products to accommodate consumer demands, additional information is needed to ensure processing methodologies result in safe eggs from all egg sources. A study was conducted to determine if there were differences in the prevalence of coliforms, Salmonella, Listeria, and Campylobacter on and within eggs and in the environment of a sister flock of conventional cage and free range laying hens. Microbial sampling occurred approximately every six weeks between 20-79 wks of age. A random sampling of typical coliform colonies produced 371 viable isolates for biochemical identification. Twenty-nine genus or species of bacteria were identified. There was a significantly greater (P < 0.0001) prevalence of Campylobacter in the free range nest box swabs (FRNS) compared to free range grass (FRG) and conventional cage swab (CS) samples (number of positives: 8 FRNS; 1 FRG; 0 CS). Seven isolates of Listeria innocua were detected with no significant difference in prevalence between the treatments. Isolates were associated with egg shells (2 free range floor; 1 cage) and the free range environment (2 FRNS; 2 FRG). There were twenty-one Salmonella isolates detected between all sample locations; with no significant difference in the prevalence of Salmonella detection between the treatments. Additional studies are needed to fully understand the impact of alternative production methods on the prevalence of pathogens and coliforms associated with nest run eggs and the production environment.