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United States Department of Agriculture

Agricultural Research Service

Related Topics

Research Project: MICROBIOLOGICAL COMPARISON OF TABLE EGGS HARVESTED FROM CAGED LEGHORN HENS AND CAGE-FREE FLOOR REARED LEGHORN HENS

Location: Poultry Microbiological Safety Research

2009 Annual Report


1a.Objectives (from AD-416)
Compare the microbiology of eggs obtained from caged Leghorn hens and cage-free floor housed Leghorn hens with both naturally contaminated and artificially inoculated environments.


1b.Approach (from AD-416)
Day of age Leghorn pullets will be obtained and reared in a confinement rearing facility set up to industry standards until the birds reach sexual maturity. At this time, a confinement housing facility would be set up to simulate a commercial Leghorn setting where the hens are housed in cages versus a confinement rearing facility where Leghorn hens are housed on the floor and eggs collected from nest boxes. To test the microbiology of the eggs from the two laying areas, an assortment of microbiological analyses (i.e. total aerobic plate count, Enterobacteriaceae count, E. coli count, Campylobacter, and Salmonella) of the eggs from both groups will be performed. In addition, another set of experiments will be conducted where the Leghorn hens are inoculated and colonized with a Naladixic acid resistant Salmonella and analysis of the eggs conducted.


3.Progress Report

This project is related to Objective 2 of this in-house project: This research quantifies the bacteria levels recovered from table eggs produced in three laying environments prior to and following eggshell sanitization and has implication for foodborne pathogens associated with table eggs.

The bacteria levels of non-washed and washed eggs obtained from caged and cage-free hens housed in either all wire slats or all shaving-covered pens were determined over an 8 month production period. On each sample day (from 22 to 52 wk), 20 eggs were collected from each pen (n=120/sample day). Ten eggs/pen were washed for 1 min with a commercial egg washing solution (50 C, pH 11, 5 psi), while the remaining 10 eggs were not washed prior to sampling the eggshell and membranes (crush-and-rub) for aerobic bacteria (APC), Escherichia coli (E. coli ), and coliforms. Non-washed eggs produced in an all shavings environment had slightly higher bacteria numbers (APC 4.0 and coliforms 1.1 log10 cfu/mL of rinsate) than eggs produced on slats (APC 3.6 and coliforms 1.0 log10 cfu/mL), which had significantly higher bacteria numbers than eggs produced in cages (APC 3.1 and coliforms 0.88 log10 cfu/mL). Washing significantly reduced APC counts by 1.7 log10 cfu/mL, and APC prevalence was reduced from 100, 99, and 98% (shavings, slats, and cages, respectively) to 87% for shavings and to 68% for caged and slat hens. Washing significantly reduced coliform counts by 0.5 log10 cfu/mL and prevalence was reduced from 22.5, 17.5, 12.5% (shavings, slats, and cages, respectively) to 6%. No significant differences were found in APC, E. coli, and coliform counts on eggs from the three housing types after the eggs were washed. These results indicate that eggshell bacteria levels are similar following washing for eggs from hens housed in these cage and cage-free environments.

Scientist attended and participated in monthly meetings and facilities visits to discuss and monitor research activities.


Last Modified: 4/17/2014
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