Location: Egg and Poultry Production Safety Research Unit
2020 Annual Report
Objectives
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.
Approach
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.
Progress Report
Internal organ colonization and horizontal transmission by Salmonella Enteritidis and Salmonella Kentucky by experimentally infected laying hens in cage-free indoor housing after prior vaccination. A study was completed to determine the frequency at which these highly prevalent Salmonella serovars were deposited inside the edible contents of eggs laid by groups of previously vaccinated, experimentally infected laying hens in a housing system which is becoming increasingly prominent in the egg industry.
Detection of Salmonella, Campylobacter, and Listeria in cage-free aviary environmental swabs. A study was completed to determine the detection of naturally occurring pathogens, as well as the ability to detect low level Salmonella Enteritidis inoculation in a variety laying hen environmental swabs. Drag swabs and manure scraper swabs (the currently mandated environmental swab types), as well as nest box swabs and egg belt, wall, and concrete flooring dust samples were collected for the comparison.
Comparison of egg physical, functional and microbial quality from around the world. Eggs imported from Turkey and India, as well as domestic eggs, were held for 42-45 days post-lay under refrigeration before assessing for Salmonella prevalence, as well as egg quality. A full complement of physical and functional egg quality characteristics were monitored.
Cage-free forage substrate material influence on pathogen shedding and environmental microbiology. Utilization of shavings or astroturf (with manure removal system) as forage material in a cage-free laying pullet housing system was compared for microbiological impact. Each month, drag swabs were assessed for Salmonella spp. prevalence and enumeration of coliforms. Up to 5 colonies from each positive coliform sample were randomly selected, cleaned, and stored for identification to determine microbial diversity at the end of the project. This study was replicated and completed.
Internal organ colonization and vertical transmission by Salmonella Braenderup by experimentally infected laying hens in cage-free housing. A study has been initiated to determine the ability of the egg-associated human outbreak strain of Salmonella Braenderup to colonize organs and vertically transmit into eggs laid by experimentally inoculated cage-free laying hens.
Development of training materials for shell egg processing facility pre-operational sanitation assessment. In collaboration with USDA AMS and Purdue University, video footage collected during FY 19 is being utilized to develop online training content for both USDA AMS shell egg inspectors and egg processors. Six training videos are now available free access. The project is ongoing.
Accomplishments
1. Internal organ colonization and horizontal transmission by Salmonella Enteritidis and Salmonella Kentucky by experimentally infected laying hens in cage-free indoor housing after prior vaccination. Laying flocks are often vaccinated to protect against Salmonella Enteritidis infections which can be transmitted to humans when infected hens lay contaminated eggs, but the ongoing transition of the commercial egg industry toward the use of non-cage housing options has raised new questions about the food safety consequences of egg production practices. ARS researchers in Athens, Georgia, assessed the horizontal transmission of Salmonella infection and invasion of internal organs after experimental infection of previously vaccinated laying hens housed on wood shavings in isolation rooms simulating commercial cage-free barns with nest boxes and perches. One-third of the hens in each room received either S. Enteritidis or S. Kentucky (a common environmental strain but not associated with egg-borne disease transmission) and all were evaluated 12 d after infection to detect the presence of Salmonella in internal organs. After S. Enteritidis infection, pathogen colonization was detected in the intestines, livers, and spleens of 67% of orally inoculated hens and also in the intestines and livers of some uninoculated birds (exposed by horizontal contact). Significantly fewer hens were colonized by S. Kentucky. These results demonstrate that vaccines may not always provide complete exclusion of Salmonella, especially highly invasive serovars like S. Enteritidis, so a comprehensive risk reduction effort should be used to supplement vaccination of hens in cage-free housing systems to prevent extensive horizontal dissemination of Salmonella infection.
Review Publications
Gast, Richard K. and Robert E. Porter, Jr., 2020. Salmonella infections. Pages 719-753 in Diseases of Poultry, 14th edition. D. E. Swayne, ed. John Wiley and Sons, Hoboken, New Jersey.
Jones, D.R., Gast, R.K., Regmi, P., Ward, G.E., Anderson, K.E., Karcher, D.M. 2020. Pooling of laying hen environmental swabs and efficacy of Salmonella spp. detection. Journal of Food Protection. 83(6):943-950.
Weimer, S.L., Robison, C.I., Tempelman, R.J., Jones, D.R., Karcher, D.M. 2019. Laying hen production and welfare in enriched colony cages at different stocking densities. Poultry Science. 98:3578-3586.
