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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

2017 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 in commercial aviary housing system on egg quality and functionality. A study was completed 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 wk and assessed every 4 wk. The study was conducted for a full 50 wk production cycle. Duration 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 completed. Affect of early lay phase and genetic strain in cage-free production system on egg physical and functional parameters. A study was conducted to assess when during early lay phase consistent egg physical and functional quality data could be attained. Beginning at 19 wk of age, eggs were evaluated each week thru 25 wk of age. Three genetic lines each of brown and white egg layers were compared. A full profile of egg physical and functional quality measurements were conducted each week. Influence of genetic strain and housing system on egg and environmental microbiology. A study was initiated to determine the impact of 4 hen housing systems and 3 genetic strains of laying hens on egg and environmental microbiology. Samples are being collected every 8 wk from a collaborative commercial style research farm. Indicator populations (total aerobes, Enterobacteriaceae, and yeasts and molds) are enumerated. Pathogen (Salmonella, Campylobacter, and Listeria) prevalence is also being determined. The project will be conducted from 20 – 68 wk of age. Influence of genetic strain and housing system on pathogen shedding. A study is in progress to determine the impact of 4 housing systems and 3 genetic strains of laying hens on Salmonella, Campylobacter, and Listeria shedding. Beginning at hatch, fecal samples are collected monthly and assessed for pathogen prevalence. The assessment will be conducted from hatch – 68 wk of age. Egg physical quality across hen housing systems and genetic strains. A study is in progress assessing the impact of 4 hen housing systems and 3 genetic strains of laying hens on egg physical quality parameters. Bi-monthly egg samples are evaluated for egg shape, shell characteristics, interior quality, and yolk physical characteristics. This study will be conducted from 20 – 68 wk of age. Hen housing system influence on egg functional quality. A study is in progress examining the influence of hen housing system on functional characteristics of eggs. Eggs from a single genetic brown egg strain of laying hen are collected bi-monthly and assessed for foaming, emulsification, and coagulation functions in food matrices. Consumer quality traits are also compared. The study will be conducted from 20 – 68 wk of age. Survival and multiplication of genetically characterized Salmonella Enteritis strains in egg yolk and albumen. A study of the growth of a set of S. Enteritidis isolates (with defined genetic differences in properties related to their ability to infect chickens and deposit inside forming eggs) in experimentally contaminated egg contents was completed. Invasion of internal organs by Salmonella Enteritidis in commercial genetic lines of laying hens housed in conventional or enriched colony cages. A study to determine the frequency at which this epidemiologically important Salmonella serotype infected tissues of experimentally infected laying hens representing four genetically distinct commercial lines (housed in two different caging systems) was completed. Effectiveness of manure drag swab pooling on the detection of Salmonella spp. A study is underway to determine the effectiveness of various pooling scheme on the effective detection of Salmonella spp. in federally required manure drag swab samples. This study is being conducted in conjunction with the Food and Drug Administration (FDA). Egg processing and holding conditions impact on egg physical quality during extended storage. A study is underway to determine the influence of various shell egg processing methods and storage temperature on egg physical quality during extended storage. Each week, eggs from various processing and holding conditions are assessed for physical quality characteristics. This study is conducted in partnership with the egg industry, as well as USDA Agricultural Marketing Service (AMS), to address international shell egg import and export limitations. On-farm holding of pullets during quarantine conditions and resulting egg quality. A study was conducted to determine the influence of various strategies for holding pullets on-farm during disease quarantine conditions and the resulting impact on egg physical quality. A full profile of physical egg quality parameters were assessed during the on-farm holding phase and subsequent move to cage-free aviary housing.


4. Accomplishments
1. Duration of fecal shedding of Salmonella (S.) Enteritidis by experimentally infected laying hens housed in enriched cages at different stocking densities. ARS researchers in Athens, Georgia, determined that housing laying hens in enriched colony cages at a higher stocking density increased the frequency at which they shed S. Enteritidis in their feces after being experimentally infected, but housing hens in conventional cages caused an even higher frequency of shedding. In recent years, alternatives to conventional cage-based housing for poultry flocks have become increasingly common in the commercial egg industry, but the impact of different housing systems on important public health problems, such as S. Enteritidis contamination of eggs laid by infected hens, are not yet fully understood. In this study, laying hens were housed in colony cages enriched with perches and enclosed nesting areas at two different stocking densities (defined by the amount of floor space available to each bird), or in conventional cages at the higher density, and infected orally with S. Enteritidis. Samples of voided feces were collected from trays beneath the cages at weekly intervals and tested for the pathogen. The frequency of S. Enteritidis isolation from feces was significantly greater when infected hens were housed in enriched colony cages at the higher stocking density in comparison to the lower density, but S. Enteritidis was isolated from fecal samples at a greater overall frequency from hens in conventional cages than from either group housed in enriched cages. These results demonstrate that hen stocking density can affect the susceptibility of hens to intestinal colonization by S. Enteritidis, but some other characteristic which distinguishes conventional and enriched colony cage systems also exerts an influence.

2. Duration of fecal shedding of Salmonella (S.) Heidelberg and Salmonella Typhimurium by experimentally infected laying hens housed in enriched cages at different stocking densities. ARS researchers in Athens, Georgia, determined that housing laying hens in different cage systems or at different stocking densities affected the frequency at which infected hens shed S. Heidelberg, but not S. Typhimurium, in their feces. Although alternatives to conventional cage-based housing for poultry flocks have become increasingly common in the commercial egg industry, their impact on the important food safety problem of Salmonella contamination of eggs remains incompletely understood. In this study, laying hens were housed in colony cages enriched with perches and enclosed nesting areas at two different stocking densities (defined by the amount of floor space available to each bird), or in conventional cages at the higher density, and infected orally with either S. Heidelberg or S. Typhimurium (Salmonella serovars known to cause egg-transmitted human illness). When samples of voided feces were collected from trays beneath the cages at weekly intervals, S. Heidelberg was found in the feces of infected hens for more weeks after inoculation and at a higher overall frequency than was S. Typhimurium. Housing did not influence the frequency of S. Typhimurium shedding, but hens in both higher stocking density cage groups (enriched colony and conventional) shed S. Heidelberg at a greater frequency than did hens in enriched colony cages at the lower density. These results demonstrate that stocking density can influence the fecal shedding of Salmonella by laying hens for some (but not all) serovars or strains.


Review Publications
Gast, R.K., Guraya, R., Jones, D.R., Anderson, K.E., Karcher, D.M. 2017. Frequency and durationn of fecal shedding of Salmonella Enteritidis by experimentally infected laying hens housed in enriched colony cages at different stocking densities. Frontiers in Veterinary Science. 4:47.
Hudson, L., Harrison, M., Berrang, M.E., Jones, D.R. 2016. Alternative antimicrobial commercial egg washing procedures. Journal of Food Protection. 79:1216-1220.
Gast, R.K. 2016. Microbiology of Shell Egg Production in the United States. In Producing Safe Eggs, Steven C. Ricke and Richard K. Gast, eds. Academic Press, London, UK. p. 25-44.
Gast, R.K., Guraya, R., Jones, D.R., Guard, J.Y., Anderson, K.E., Karcher, D.M. 2017. Colonization of internal organs by Salmonella serovars Heidelberg and Typhimurium in experimentally infected laying hens housed in enriched colony cages at different stocking densities. Poultry Science. 96:1402-1409.
Gast, R.K. 2017. Sampling and detection of Salmonella in eggs. In Achieving Sustainable Production of eggs: Volume 1: Safety and Quality, J. Roberts, Ed. Burleigh Dodds, Cambridge, UK. p.141-160.
Gradl, J.A., Curtis, P.A., Jones, D.R., Anderson, K.E. 2017. Assessing the impact of egg sweating on Salmonella Enteritidis penetration into shell eggs. Poultry Science. 96:2393-2399.
Jones, D.R. 2017. The effects of housing systems for laying hens on egg safety and quality. In Achieving Sustainable Production of eggs: Volume 1: Safety and Quality, J. Roberts, Ed. Burleigh Dodds, Cambridge, UK. p.195-210.
Hofacre, Charles, L., Randall Singer, and Richard K. Gast, 2017. Foodborne Salmonella control. In: A Practical Guide for Biosecurity in the Poultry Industry, 2nd edition. Jacksonville, FL. Robert L. Owen, ed., pp. 53-59.
Waltman, W. Douglas and Richard K. Gast, 2016. Salmonella enterica. In Isolation and Identification of Avian Pathogens, 6th edition, S. M. Williams, L. Dufour-Zavala, M. W. Jackwood, M. D. Lee, B. Lupiani, W. M. Reed, E. Spackman, and P. R. Woolcock, eds.American Association of Avian Pathologists, Athens, GA. pp. 103-112.
Gast, R.K., Jones, D.R. 2017. Salmonella and impact on egg production. In Egg Production: Innovations and strategies for improvement, Patricia Hester, ed., Academic Press, Cambridge, MA. pp. 513-522.