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United States Department of Agriculture

Agricultural Research Service

Related Topics

Research Project: Microbiological and Product Quality Consequences of Housing Laying Hens in Production Systems

Location: Egg Safety and Quality

2013 Annual Report


1a.Objectives (from AD-416):
1. Evaluate the role of various production and management systems and storage and processing practices on egg safety (and quality). This project focuses on critical points that may influcence USDA shell egg grade standards and federally mandated conditions.

2. Evaluate the role of various production and management systems on the detection, transmission, and persistence of Salmonella spp. in eggs and the surrounding production environment (e.g. flocks and house contamination).

3. Evaluate the role of various production and management systems on the effectiveness of shell egg processing guidelines utilized in the U.S.


1b.Approach (from AD-416):
Egg safety and quality issues often initiate in production and storage before entering the processing facility. There is a need for a farm-to-fork approach to product safety and quality, especially in light of new federal regulations and increased interest in alternative housing systems to replace housing hens in cages. Research will serve today’s fully integrated and streamlined egg industry most effectively if it covers the full scope of egg production to processing. Additionally, strategies to assist small flock egg producers enhance product safety and quality will also be developed. These goals will be accomplished by assessing the role of production systems on naturally occurring flora and pathogens in and on shell eggs, evaluating the effects of federally mandated storage conditions on the microbial and physical quality of eggs from various production systems, and developing processing and storage options for small flock egg producers to ensure egg safety and quality. The poultry house environment plays a highly significant role in Salmonella infections of laying flocks. This research will determine how different production systems for housing laying hens affect the transmission and persistence of experimentally introduced Salmonella infection or house contamination and the associated frequency and nature of egg contamination. It will also determine how different production systems affect the detection of Salmonella in laying flocks and their housing environment, and evaluate the performance of testing methodologies for detecting S. Enteritidis and other Salmonella spp. in flocks and eggs from different production systems to develop rapid, sensitive, and cost-effective testing strategies.


3.Progress Report:
Comparing egg quality from hens housed in various commercial production systems. A study monitoring the quality of eggs produced commercially from conventional and enriched cage, as well as aviary systems was completed. Monthly, eggs were monitored for shell and component physical quality. Quarterly, eggs were washed and stored at 4C to determine rate of quality decline over 12 wks.

Comparing egg and environmental microbiology of hens housed in various commercial production systems. Completed study sampling production environments and eggs from conventional cage, enriched cage, and aviary systems. Monitored total aerobes and coliforms, as well as prevalence of Salmonella and Campylobacter.

Multiplication of Salmonella Enteritidis in egg yolks during the first 24 h of refrigeration at 7.2C. A study using experimentally contaminated egg yolks to determine the survival and multiplication of S. Enteritidis during the first day of transfer into refrigerated storage conditions was completed.

Salmonella Enteritidis contamination of eggs laid by experimentally infected laying hens housed in conventional or enriched cages. A study of the frequency of internal contamination in eggs laid by experimentally infected hens housed in conventional and enriched cages was completed.

Horizontal transmission of experimental Salmonella Enteritidis infection in laying hens housed in conventional or enriched cages. A study of the horizontal transmission of infection within groups of hens housed in conventional and enriched cages was partially completed.

Impact of high and low paddock stocking density on egg and environmental microbiology in free range production. A study was completed comparing access to high or low density paddock spacing on egg and environmental microbiology. Levels of total aerobes, Enterobacteriaceae, and yeasts and molds were determined, as well as presence of Salmonella, Campylobacter, and Listeria.

Sustainable grazing effects on egg and environmental microbiology under organic management. A study was completed examining the impact of sustainable grazing behind organic dairy on microbiology associated with organic egg production. Levels of total aerobes, Enterobacteriaceae, and yeasts and molds were determined, as well as presence of Salmonella, Campylobacter, and Listeria. The diversity of Enterobacteriaceae cultured was also determined.

Nest box and scratch area substrate effects on egg microbiology in free range and aviary production systems. Through collaborations with NC State and Michigan State, studies are underway monitoring egg microbiology and the incidence of Salmonella, Campylobacter, and Listeria associated with nest box and scratch area substrate, respectively. Astroturf, straw, and shavings are being compared.

Hen density impacts on egg quality in enriched cage production. A new collaboration was begun with Michigan State examining the impact of hen stocking density in enriched colony cage production on egg quality. Egg physical quality and yolk color parameters are monitored for hens in two commercial housing systems at 6 different stocking densities.


4.Accomplishments
1. Salmonella Enteritidis deposition in eggs after experimental infection of laying hens with different oral doses. ARS researchers in Athens, Georgia determined that infecting egg-laying hens with increasing oral doses of Salmonella Enteritidis led to both a significantly higher percentage of internally contaminated eggs and a shift toward more eggs having albumen contamination (in addition to or instead of yolk contamination). Governments and the poultry industry continue to devote substantial resources to controlling S. Enteritids contamination of eggs by testing and risk reduction programs for commercial laying flocks, but effective disease control requires a comprehensive understanding of the process by which contaminated eggs are produced. In the present study, groups of laying hens were experimentally infected with different oral amounts (doses) of S. Enteritidis in order to investigate any dose effects on the frequency and location of contamination in eggs laid by these birds. The results of this study demonstrate that the effectiveness of important risk reduction practices such as refrigeration can be influenced by the dose of S. Enteritidis that laying hens are exposed to from their environment.

2. Colonization of internal organs by Salmonella Enteritidis in experimentally infected laying hens housed in conventional or enriched cages. ARS researchers in Athens, Georgia determined that two types of housing systems for laying hens (conventional and enriched cages) did not affect the frequency of colonization of the intestinal tract after experimental oral infection with Salmonella Enteritidis, but the pathogen was found at a significantly higher frequency in liver, spleen, ovary, and oviduct samples from hens in conventional cages than from hens in enriched cages. The majority of human illnesses caused by Salmonella Enteritidis have been linked to the consumption of contaminated eggs produced when this organism colonizes the reproductive organs of laying hens, but the food safety consequences of different types of housing systems used for commercial egg-laying flocks are not yet clear. In the present study, two different types of housing (conventional cages and enriched colony cages with perches and enclosed nesting areas) were evaluated for their effects on internal organ colonization in laying hens infected orally with S. Enteritidis. These results demonstrate that differences in housing systems for egg-laying flocks can affect the susceptibility of hens to infection and internal organ colonization by S. Enteritidis.


Review Publications
Jones, D.R., Broussard, V., Lawrence, K.C., Yoon, S.C., Heitschmidt, G.W. 2012. Dynamic and Static Shell Properties of White and Brown Shell Eggs Exposed to Modified-pressure Microcrack Detection Technology. Poultry Science. 91:2658-2661.

Jones, D.R., Anderson, K.E. 2013. Housing system and laying hen strain impacts on egg microbiology. Poultry Science. 92:2221-2225.

Gast, R.K., Guraya, R., Jones, D.R., Anderson, K.E. 2013. Colonization of internal organs by Salmonella Enteritidis in experimentally infected laying hens housed in conventional or enriched cages. Poultry Science. 92:468-473.

Gast, R.K., Guraya, R., Guard, J.Y. 2013. Salmonella Enteritidis deposition in eggs after experimental infection of laying hens with different oral doses. Journal of Food Protection. 76:108-113.

Last Modified: 7/22/2014
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