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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

2010 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 research relates to inhouse objective 2: Identify host and pathogen genes important to colonization and/or toxin formation by Campylobacter jejuni and Clostridium perfringens in poultry, and monitor host and pathogen gene expression by RNA microarray analysis. Complete comparative genomic analyses between robust and poor colonizers to identify gene targets that could be disrupted to decrease pathogen presence in the gut environment.

In Experiment 2, non-washed eggs produced by hens moved to triple-deck cages from 57 to 62 weeks of age (previously housed on shavings, slats, and cages from 22 to 52 weeks of age in Experiment.
1)did not differ with aerobic bacteria levels from 0.67 to 0.84 log10cfu/mL. Washing eggs continued to significantly reduce bacteria levels to below 0.2 log10cfu/mL. In Experiment 3, from 56-72 weeks of age when hens were moved back into the previous housing environments on shavings, slats, or in cages without cleanout, the levels of bacteria for non-washed eggs were within 0.4 log below the values attained for non-washed eggs in Experiment 1 (from 22 to 52 weeks of age), although hens in Experiment 3 were at 28% of the hen density used in Experiment 1. Washing eggs further lowered bacteria levels to 0.4-0.7 log10cfu/mL, a 2.7 log reduction. These results indicate that eggshell bacteria levels are similar following washing for eggs from hens housed in these cage and cage-free environments (shavings and slats). However, housing hens in cages with manure removal belts resulted in lower aerobic bacteria levels for both non-washed and washed eggs (compared to eggs from hens housed in a room with shavings, slats, and cages) and corresponding reductions in human pathogens would further improve food safety. The impact of this research project for the U.S. egg industry is documentation that eggs produced by hens in cage-free environments that contain shavings will have higher eggshell bacteria levels. However, following washing eggs with small scale commercial style egg processing equipment, washed eggs became indistinguishable regarding the housing system from which the eggs were produced or the strain of hen that laid them. Scientist attended and participated in monthly meetings and facilities visits to discuss and monitor research activities.


Last Modified: 8/29/2014
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