Skip to main content
ARS Home » Southeast Area » Athens, Georgia » U.S. National Poultry Research Center » Egg Safety & Quality Research » Research » Research Project #430344

Research Project: Evaluation of Management of Laying Hens and Housing Systems to Control Salmonella and Other Pathogenic Infections, Egg Contamination, and Product Quality

Location: Egg Safety & Quality Research

2016 Annual Report


1a. Objectives (from AD-416):
Objective 1: Assess the impact of dietary regimens, housing systems, and different chicken genetic lines on Salmonella (S.) infections of hens, Salmonella contamination of the production environment and eggs, and physical and functional egg quality. 1.a. Holistic comparison of genetic strains in commercial cage-free aviary housing. 1.b. Compare Salmonella shedding and microbial quality of eggs and environment in commercial-style conventional cage, enriched colony cage, enrichable colony cage, cage-free, and free range systems for various genetic strains of laying hens. 1.c. Assess the susceptibility of defined genetic lines of laying hens to infection with S. Enteritidis when housed in different cage-based production systems. Objective 2: Assess the effects of key management practices using experimental and field models of different housing systems on hen health, microbial ecology of foodborne bacteria, and antimicrobial resistance associated with egg contamination. 2.a. Assess the effects of different stocking densities on S. Enteritidis infections in laying hens housed in enriched colony cages. 2.b. Assess the effects of different cage-based housing systems on infections of laying hens with Salmonella serotypes (other than Enteritidis) which are significantly associated with egg contamination. 2.c. Determine the impact of hen housing systems on prevalence, diversity, and antimicrobial resistance of Salmonella, Campylobacter, Listeria, and Enterobacteriaceae associated with the production environment and eggs.


1b. Approach (from AD-416):
The housing of laying hens has become a matter of state and federal regulatory concern, as well as a purchasing consideration for consumers. While the shift in European Union laying hen housing requirements resulted in a plethora of research, most have limited similarity to the management systems utilized in the U.S. This project will, through national collaborative efforts, examine the impact of U.S. commercial hen housing systems on hen health and well-being, egg and environmental microbiology, and Salmonella infection and transmission. The collaborations associated with this project allow for a comprehensive examination of hen housing systems in a cost-effective manner. Furthermore, the project incorporates the research gaps identified by federal and state regulatory groups, as well as large and small egg producers. The research project will determine the impact of hen housing systems and laying hen genetic strain on the prevalence of Salmonella, as well as other human pathogens. Additionally, this project will determine the infection rate and transmission of various Salmonella strains within these housing systems. The effects of housing and management strategies on egg quality will also be assessed. The data generated from the project can be utilized by large and small egg producers to develop informed production management plans and state and federal regulatory groups to determine regulatory needs to ensure safe, high quality eggs reach consumers.


3. Progress Report:
Impact of genetic strain on Salmonella shedding in commercial aviary housing systems. Study was initiated to determine the impact of 4 genetic strains of laying hens on Salmonella shedding from day of hatch through a full egg production cycle. Fecal shedding is monitored monthly through rearing and laying phases. Impact of genetic strain in commercial aviary housing system on egg quality and functionality. Study was initiated to assess the physical and functional quality of eggs from 4 genetic strains of laying hens housed in commercial aviary systems. Eggs are stored for 12 weeks and assessed every 4 weeks. The study will be conducted for a full production cycle. Impact of genetic strain in commercial aviary housing system on egg microbiology. Study was initiated to assess the impact of genetic strain on the levels of total aerobe, Enterobacteriaceae, and yeast and molds in shell emulsions. Nestbox, system, and floor eggs are assessed separately. The prevalence of Salmonella is also being determined. Invasion of internal organs by Salmonella Heidelberg and Salmonella Typhimurium in experimentally infected laying hens housed in enriched colony cages at different stocking densities. A study to determine the frequency at which these epidemiologically important serotypes of Salmonella colonize the internal organs of experimentally infected hens (housed at a range of stocking densities in different caging systems) was completed. Persistence of fecal shedding of Salmonella Enteritidis by experimentally infected laying hens housed in enriched cages at different stocking densities. A study of the frequency and duration of fecal shedding of the pathogen by groups of hens housed in enriched colony cages at two different stocking densities was completed. Persistence of fecal shedding of Salmonella Heidelberg and Salmonella Typhimurium by experimentally infected laying hens housed in enriched cages at different stocking densities. A study of the frequency and duration of fecal shedding of these pathogen by groups of hens housed in enriched colony cages at two different stocking densities was partially completed.


4. Accomplishments
1. Invasion of internal organs by Salmonella (S.) Enteritidis in experimentally infected laying hens housed in enriched colony cages at different stocking densities. ARS researchers in Athens, Georgia, determined that housing laying hens in enriched colony cages at different stocking densities significantly affected the progress of experimentally introduced infections with Salmonella Enteritidis, although an even greater difference was observed when hens were housed at a higher stocking density in conventional cages. Most human illnesses caused by S. Enteritidis are attributed to contaminated eggs produced by infected hens, so the recently intensified interest in alternative production housing systems for commercial laying flocks (including various types of cage-based and cage-free options) has raised many questions about the influence of poultry housing and management systems on Salmonella infections and egg contamination. This ARS research examined some of the microbiological consequences of housing laying hens in colony cages, enriched with perches and enclosed nesting areas, at different stocking densities (defined by the amount of floor space available to each bird). Groups of hens were housed at two different stocking densities (and a third group was placed in conventional cages at the higher density). S. Enteritidis infection was initiated and the birds were euthanized the following week so tissues samples could be collected and tested. S. Enteritidis was recovered more frequently from livers and ovaries of hens in enriched colony cages at the higher stocking density than at the lower density. However, S. Enteritidis was also recovered more often from spleens of hens in conventional cages than from those in enriched colony cages at the higher stocking density. These results demonstrate that stocking density can influence the susceptibility of hens to S. Enteritidis, but other characteristics of the various housing systems may also play important roles.


5. Significant Activities that Support Special Target Populations:
Research on the impact of alternative housing systems on egg safety and quality will assist small and very small egg producers in the U.S. The data generated from these projects will be incorporated into training programs through collaborations with university extension specialists in attempts to reach small U.S. farmers. Additionally, outreach presentations were made to small producer groups at various meetings and conferences throughout the year.


Review Publications
Gast, R.K., Guraya, R., Jones, D.R., Anderson, K., Karcher, D.M. 2016. Colonization of internal organs by Salmonella Enteritidis in experimentally infected laying hens housed in enriched colony cages at different stocking densities. Poultry Science. 95:1363-1369.