Submitted to: Poultry Science
Publication Type: Peer reviewed journal
Publication Acceptance Date: 1/4/2011
Publication Date: 8/18/2011
Citation: Jones, D.R., Anderson, K.E., Musgrove, M.T. 2011. Comparison of environmental and egg microbiology associated with conventional and free range laying hen management. Poultry Science. 90:2063-2068. Interpretive Summary: US consumers are demonstrating increased interest in production choices for their agricultural products. The egg industry has embraced this interest and is offering eggs from a variety of sources including: conventional cages, cage free, free range, free roaming and others. While research has been conducted on the microbial implications of various egg production practices, much of which is out of Europe, the results are conflicting. Furthermore, climate, genetic strain of laying hen, and production practices differences can all affect the microbial status of eggs making it difficult to draw clear correlations between these studies and US alternative egg production methods. A study was undertaken to compare environmental and egg microbiology associated with conventional and free range egg production. A sister flock of brown egg laying hens was maintained for a complete (79 wk) production cycle on a single research farm. The only difference between the treatments was the housing environment. Free range floor eggs experienced the greatest coliform and yeast and mold contamination of the shells. Conventional cage eggs had the highest degree of shell aerobic contamination but the lowest level of aerobic environmental contamination. The season of the year had a significant effect on the levels of aerobic microorganisms, coliforms and yeasts and molds detected in the laying environment and on the egg shells. Understanding the differences in microbial populations present on conventional cage and free range produced eggs can lead to the development of effective cleaning procedures, enhancing food safety.
Technical Abstract: Eggs from alternative production practices are a growing niche in the market. Meeting consumer requests for greater diversity in retail egg options has resulted in some unique challenges such as understanding the food safety implications of eggs from alternative production practices. A study was conducted to determine what, if any, differences exist between nest run conventional cage and free range produced eggs. A sister flock of brown egg layers were maintained in conventional cage and free range production with egg and environmental sampling every 6 wks from 20-79 wks of age. Aerobic, coliform, and yeast and mold populations were monitored. Environmental microbial levels were not always indicative of egg contamination levels. When significant differences (P < 0.05 and P < 0.0001, dependent on season) were observed amongst treatments for coliforms, free range nest box (FRNB) and free range floor (FRF) shell contamination levels were always greater than conventional cage (CC) eggs, which remained low throughout the study (0.42-0.02 log cfu/mL). FRF shell yeast and mold levels were significantly greater than FRNB and CC throughout the entire study. Egg contents contamination levels were extremely low for all monitored populations and treatments. Season of the year played a role for both environmental and egg microbial levels. Winter had the lowest levels of all populations monitored for all treatments, except for aerobic free range floor shell emulsions which were elevated (3.6 log cfu/mL). Understanding the differences in microbial populations present on conventional cage and free range produced eggs can lead to the development of effective cleaning procedures, enhancing food safety.