Location: Egg and Poultry Production Safety Research Unit
2021 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
This is the final report for this project; please refer to new project 6040-32420-003-000D, "Reducing Pathogen Contamination Risks and Improving Quality Attributes of Eggs and Egg Products through Housing System Management and Egg Handling Practices."
Egg contamination by Salmonella Enteritidis and Typhimurium in experimentally infected laying hens in cage-free indoor housing. A study was completed to determine the frequency at which these highly invasive and prevalent Salmonella serovars were deposited inside the edible contents of eggs laid by infected laying hens in a housing system which is becoming increasingly prominent in the egg industry.
Egg handling and ambient temperature impacts on physical and microbial quality during extended storage. The impact of handling practices in the shell egg processing facility, as well as post-processing ambient storage temperature on physical and microbial quality of eggs during 6 months of storage is being assessed. The study is necessary for USDA AMS to set shell egg import and export certification standards.
Validation of USDA AMS sampling rates in official shell egg processing facilities. A study is underway, in conjunction with Purdue University, to determine if current USDA AMS sampling rates (1 in every 100 cases) are effective and efficient at maintaining USDA AMS shell egg grading standards.
Development of instrument enhanced grading parameters for shell eggs in USDA AMS shell egg processing facilities. The validation stage of a long-term study, in conjunction with AMS and Purdue University, is currently underway to determine machine settings for large capacity shell egg processing equipment that will ensure packaged product meets shell egg grade standards.
Internal organ colonization and horizontal transmission by Salmonella Enteritidis and Kentucky by experimentally infected laying hens in cage-free housing after prior vaccination. A study was completed to determine the frequency at which these Salmonella serovars were deposited in the egg contents laid by previously vaccinated, experimentally infected cage-free laying.
Detection of Salmonella, Campylobacter, and Listeria in cage-free aviary environmental swabs. A study was completed to determine the naturally occurring pathogens, as well as the ability to detect low level Salmonella Enteritidis inoculation, in a variety of laying hen environmental swabs. Drag swabs and manure scraper swabs, as well as nest box swabs and egg belt, wall, and concrete flooring dust samples were compared.
Comparison of egg physical, functional and microbial quality from around the world. Eggs imported from Turkey and India, as well as domestic eggs, were assessed for Salmonella prevalence, as well as egg quality. A full complement of physical and functional egg quality characteristics was 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.
Internal organ colonization and vertical transmission by Salmonella Braenderup (SB) by experimentally infected laying hens in cage-free housing. A study was completed to determine the ability of the egg-associated human outbreak strain of SB to colonize organs and vertically transmit into eggs from 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 AMS shell egg graders and egg processors. Twelve free-access training videos are now available with over 5,800 views. The project is ongoing.
Influence of Northern Fowl Mites (NFM) on pathogen shedding, egg and environmental microbiology, and egg quality. NFM were introduced in a cage-free laying flock to determine if fecal shedding of Salmonella and Campylobacter spp. was influenced. Additionally, environmental swabs, egg shell emulsions, and egg contents were monitored for the two pathogens. Egg shape and volume, shell strength, egg weight, Haugh unit, vitelline membrane strength, and hard-cooked yolk strength were evaluated every 12 wks throughout the production cycle.
Determination of compounds utilized in shell egg processing in the US. USDA FSIS requested ARS assistance in determining chemicals which make direct egg contact during shell egg processing in the US. ARS coordinated efforts with USDA AMS to collect information on chemical usage at all official shell egg processing facilities. The extensive list was provided to FSIS, along with copies of all associated safety data sheets. This information was utilized to update FSIS Directive 7120.1 Rev 55.
Impact of nutrition interventions in cage-free aviary housing on egg quality. Hens in commercial cage-free aviaries were provided basal diets as well as those supplemented with various omega fatty acids or vitamin D. Egg shape and volume, weight, shell strength, Haugh unit, and vitelline membrane strength, as well as hard-cooked yolk strength and color were assessed from 20–50 wk of age.
Laying hen skeletal health impact on response to Salmonella Enteritidis (SE) challenge. Mature laying hens with low and extensive keel damage scores, based on Welfare Quality Assessment and MRI assessments were individually housed. Hens were challenged with SE and monitored for infection in liver, spleen, ceca, and magnum/isthmus junction to determine if skeletal health impacted the infection response.
Determining equivalency of peracetic acid (PAA) as a shell egg sanitizing rinse. A study was conducted to determine what concentrations of PAA were equivalent to the mandatory 100-200 ppm chlorine (Cl) post-wash rinse in reducing shell surface levels of 3 Salmonella spp. and Enterobacter cloacae. It was determined 50-100 ppm PAA reduced surface bacterial levels similar to 100-200 ppm Cl. AMS has adjusted policy to allow for this level of usage in the voluntary grading program.
Influence of genetic strain and housing system on egg and environmental microbiology and physical egg quality. The impact of 4 hen housing systems and 3 genetic strains of laying hens on egg and environmental microbiology was assessed from 20-68 wk of age. Samples were collected every 8 wk from a collaborative commercial style research farm. Total aerobes, Enterobacteriaceae, and yeasts and molds were enumerated. Salmonella, Campylobacter, and Listeria prevalence was also determined. Egg samples were evaluated for egg shape, shell characteristics, interior quality, and yolk physical characteristics.
Influence of genetic strain and housing system on pathogen shedding. The impact of 4 housing systems and 3 genetic strains of laying hens on Salmonella, Campylobacter, and Listeria shedding. Beginning at hatch to 68 wk of age, fecal samples were collected monthly and assessed for pathogen prevalence.
Deposition of Salmonella Enteritidis (SE) inside eggs produced by genetic lines of laying hens housed in conventional cages or enriched colonies. A study to determine the frequency of SE deposition in the contents of eggs laid by experimentally infected hens representing 4 genetically distinct commercial lines (in 2 different housing systems) was completed.
Hen housing system influence on egg functional quality. The influence of hen housing system on functional characteristics of eggs were examined. Eggs from a single genetic brown egg strain of laying hen were collected bi-monthly from 20-68 wk of age and assessed for foaming, emulsification, and coagulation functions in food matrices. Consumer quality traits were also compared.
Effectiveness of manure drag swab pooling on the detection of Salmonella spp. A study was concluded to determine the effectiveness of various pooling schemes on the detection of Salmonella spp. in federally required manure drag swab samples in laying hen barns. This study was conducted in conjunction with FDA.
Duration of fecal shedding of Salmonella Heidelberg and 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 pathogens by hens housed in enriched colony cages at two different stocking densities was completed.
Effect 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 (19-25 wk of age) consistent egg physical and functional quality data could be attained. Three genetic lines each of brown and white egg layers were compared. A full profile of egg physical and functional quality measurements was conducted.
Survival and multiplication of genetically characterized Salmonella Enteritis (SE) strains in egg yolk and albumen. A study of the growth of SE isolates (with defined genetic differences in their ability to infect chickens and deposit inside forming eggs) in experimentally contaminated egg contents was completed.
Invasion of internal organs by Salmonella Enteritidis (SE) in commercial genetic lines of laying hens housed in conventional or enriched colony cages. A study to determine the frequency at which SE infected tissues of inoculated laying hens representing 4 commercial lines (housed in two different caging systems) was completed.
On-farm holding of pullets during quarantine conditions and resulting egg quality. The influence of various strategies for holding pullets on-farm during disease quarantine conditions and the resulting impact on egg physical quality was studied. A full profile of physical egg quality parameters was assessed during the on-farm holding phase and subsequent move to cage-free aviary housing.
Accomplishments
1. Internal organ colonization and horizontal transmission by Salmonella Enteritidis and Salmonella Kentucky in experimentally infected laying hens in cage-free indoor housing. 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 inoculation of laying hens housed on wood shavings in isolation rooms simulating commercial cage-free barns with nest boxes and perches. After S. Enteritidis oral infection, both intestinal colonization and internal organ invasion (particularly to livers and ovaries) were detected in most orally inoculated hens, as well as in many uninoculated hens (exposed by horizontal contact with inoculated birds). After S. Kentucky oral infection, intestinal colonization was likewise observed at high frequencies in both inoculated and uninoculated hens, but invasion to internal organs was seldom detected. These results demonstrated that Salmonella infection can spread rapidly and extensively among hens in cage-free indoor housing, including a high frequency of internal organ invasion for the epidemiologically important serovar, S. Enteritidis.
Review Publications
Gast, R.K., Jones, D.R., Guraya, R., Anderson, K.E., Karcher, D.M. 2020. Horizontal transmission and internal organ colonization by Salmonella Enteritidis and Salmonella Kentucky in experimentally infected laying hens in indoor cage-free housing. Poultry Science. 99:6071-6074.
Gast, R.K., Jones, D.R., Guraya, R., Anderson, K.E., Karcher, D.M. 2021. Internal organ colonization and horizontal transmission of experimental Salmonella Enteritidis and Salmonella Kentucky infection in vaccinated laying hens in indoor cage-free housing. Journal of Applied Poultry Research. 30:100132.
Jones, D.R., Garcia, J.S., Gast, R.K., Ward, G.E. 2021. Equivalency of peroxyacetic acid to chlorine as a shell egg sanitizing rinse. Poultry Science. https://doi.org/10.1016/j.psj.2021.101069.
