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ARS Home Southeast Area Athens, Georgia U.S. National Poultry Research Center Egg and Poultry Production Safety Research Unit Research





- Gast, Richard
- 2023
- 2022
- 2021
- Publications
- Food Safety, (Animal and Plant Products) (108)

Research Project: Reducing Pathogen Contamination Risks and Improving Quality Attributes of Eggs and Egg Products through Housing System Management and Egg Handling Practices **Location:
                            Egg and Poultry Production Safety Research Unit** 2023 Annual Report **Objectives**
                                

1. Evaluate the impact of flock management strategies in cage-free and other hen housing systems on pathogen transmission and prevalence and egg microbial, physical and functional quality.
1.a. Ascertain the impact of laying hen flock management strategies on the vertical and horizontal transmission of pathogens.
1.b. Determine the influence of laying hen flock management strategies on egg microbiology and quality.
1.c. Assess the impact of egg handling practices on consumer product safety and quality.

2. Evaluate the impact of pullet rearing practices on pathogen transmission and prevalence and resulting egg microbial, physical, and functional quality.
2.a. Determine the transmission and persistence of pathogens in pullets reared under various housing practices.
2.b. Assess the prevalence of pathogens during the pullet phase under various commercial cage-free pullet management programs and resulting egg microbiology and quality.
2.c. Ascertain the influence of egg handling practices on consumer product safety and quality from hens reared under a variety commercial cage-free housing systems. **Approach**
                                

The starting point for this research program will be to determine the effects of cage-free housing systems for laying hens and cage-free pullet rearing programs, under U.S. commercial production conditions, on the prevalence of food-borne pathogens in flocks and the production environment and on the microbial, physical, and functional quality of eggs and egg products. These studies will generate a unique and comprehensive assessment of the environmental and management risk factors associated with cage-free egg production systems. This baseline information will then be applied in combination with collaborators’ data about housing conditions and management practices with the greatest potential significance as targets for risk mitigation. The output of this two-stage strategy will be a research-based guide of best management practices for extensive housing systems for the egg industry to maintain high standards of egg safety and quality. These guidelines will also allow the egg industry to make informed management decisions, based on definitive scientific data about the associated risk of individual practices, to effectively manage extensive housing systems, conduct housing sanitation, test to detect environmental contamination, reduce flock infection, and enhance processing facility sanitation. State and federal regulatory agencies will also be able to apply these guidelines to protect public health by reassessing current standards to ensure that safe, wholesome eggs and egg products reach consumers. Through collaboration with university extension personnel, outreach programs will be developed for large and small-scale cage-free egg producers. **Progress Report**
                                

Internal organ colonization by Salmonella Enteritidis in layer pullets infected at two different ages during rearing in indoor cage-free housing. A study was completed to assess horizontal transmission and invasion of internal organs by S. Enteritidis in egg-type pullets experimentally infected with the pathogen at two different ages (9 and 15 weeks) during rearing in cage-free housing and sampled 1-2 weeks later and just after the inception of egg production (21-22 weeks of age).

Impact of hen genetics on egg shape and functional characteristics. A study was completed comparing egg shape characteristics (length, width, shape index, percent length at maximum width, and volume of shell) and functional qualities (foaming capacity, foam stability, and emulsification capacity) of up to 10 different genetic lines of laying hens at set hen ages. The results of this study will aid in understanding if differences exist for egg functionality between strains of laying hens and the influence of hen age. This study is an industry partnership via the Poultry Science Foundation Giesen Undergraduate Internship program with Hy-Line International and in conjunction with a Pathways Student Intern from the University of Georgia.

Influence of hen diet on egg shape and shell quality. A study was conducted with the University of Georgia to determine the impact of laying hen dietary supplementation on egg shape and shell quality characteristics. At four hen ages, eggs were collected from hens which were then sacrificed for physiological and immunological analysis. Egg physical quality measurements will be correlated with the physiological and immunological metrics.
 
Cage-free housing system design, hen use of resources, and resulting microbial and physical egg quality. A study is underway to compare styles of cage-free housing design and hen usage of resources in the system. USDA ARS is currently monitoring Salmonella spp. shedding through the life cycle of the flock. Furthermore, beginning at approximately 25 weeks of age, environmental and egg microbiology, as well as egg physical quality is being monitored. This study is part of a NIFA IDEA grant in conjunction with Purdue University.

Cage-free housing substrate management impact on environmental and egg microbiology. A study was completed with the University of Georgia to assess the impact of various cage-free substrate management regimens and resulting air quality and microbiological impacts. USDA ARS monitored environmental and egg microbiology for indicator populations of total aerobes and coliforms, as well as detection of Salmonella and Campylobacter spp. This study was funded, in part, through a collaborate grant from the Egg Industry Center.

Egg sampling rate assessment and modeling. In collaboration with USDA AMS and Purdue University, the team utilized actual egg grading records from 25% of the official shell egg grading facilities during the two highest volume weeks of FY2020. USDA ARS designed the data selection and collection process and created the dataset of 3,800 grading lots. Purdue University conducted the statistical modeling. The outcome of the first phase of the project was presented to USDA AMS leadership in March 2022. USDA AMS has conducted a second phase trial of alternate sampling rate during 2022-2023. USDA ARS is overseeing data collection and consolidation. Purdue University will again provide statistical modeling and interpretation. This research is being funded in part by USDA AMS through an agreement with Purdue University.

Egg processing facility pre-operational sanitation assessment training modules. The completion of a multi-year collaborative project between USDA ARS, USDA AMS, and Purdue University Extension has resulted in 18 video training modules being available, free of charge, for the egg industry, regulators, and consumers. Due to industry enthusiasm and feedback, the modules have been translated and recorded in Spanish, bringing the total to 36 videos. Since being made available, over 13,500 views have occurred.
 
Utilizing orange corn in laying hen poultry feed for enhanced yolk color. A study is underway to determine the impact of genetically modified orange corn in the diets of laying hens and impact on egg production and quality. Purdue University is maintaining the flocks and conducting all hen management and production assessments. USDA ARS is accessing egg shape, physical quality and functional characteristics. This study is an industry partnership with Nutramaize and Eggland’s Best Eggs in collaboration with Purdue University.
 
Impact of orange corn on hen health and product quality throughout the production cycle. A study has begun to evaluate the impact of orange corn supplementation in laying feed on egg production and quailty. USDA ARS is monitoring egg quality and egg functionality. Purdue University is managing the flock and monitoring egg production and efficiency, as well as hen well-being. This study is funded by a NIFA SBIR awarded to Nutramaize, with USDA ARS and Purdue University as collaborators. **Accomplishments**
                                

1. Internal organ colonization by Salmonella Enteritidis in experimentally infected layer pullets reared at different stocking densities in indoor cage-free housing. Eggs laid by hens infected with Salmonella Enteritidis are known to cause food-borne human illness, but the effects of poultry management and housing conditions on the susceptibility of egg-laying flocks to S. Enteritidis infections are incompletely understood. ARS researchers in Athens, Georgia, assessed internal organ colonization and bird-to-bird (horizontal) transmission by S. Enteritidis in egg-type pullets reared at either high or low stocking densities (in terms of floor space per bird) in indoor cage-free housing and moved at 16 weeks of age to isolation rooms simulating commercial cage-free barns, with nest boxes, perches, and floors covered by wood shavings. One-third of the pullets in 2 rooms were orally infected with S. Enteritidis immediately after placement, and pullets in 2 other rooms were similarly infected at 19 weeks of age (at or near sexual maturity). Within 2 weeks after infection, internal organ samples were collected from the birds and tested to detect the presence of S. Enteritidis. The frequency at which the pathogen was found in tissues did not differ significantly between groups of pullets reared at high and low stocking density following infection at either age. However, S. Enteritidis was isolated significantly more often in internal organ samples collected from groups of birds infected at 19 weeks of age than from those infected at 16 weeks. These results suggest that the susceptibility of young hens to invasive S. Enteritidis infection may increase around the time of reproductive maturity, emphasizing the importance of comprehensive risk reduction at this critical stage in the egg production cycle. 2. Internal organ colonization by Salmonella Enteritidis in experimentally infected layer pullets reared in conventional cage or cage-free housing. Eggs contaminated by Salmonella Enteritidis are often implicated as sources of food-borne human illness and the transition of the commercial egg industry from traditional cage-based housing to cage-free systems has raised questions about potential ramifications for food safety. ARS researchers in Athens, Georgia, assessed internal organ colonization and bird-to-bird (horizontal) transmission by S. Enteritidis in egg-type pullets reared in 2 different housing systems (conventional cages and cage-free floor pens) and moved at 16 weeks of age to isolation rooms simulating commercial cage-free barns, with nest boxes, perches, and floors covered by wood shavings. One-third of the pullets in 2 rooms were orally infected with S. Enteritidis immediately after placement, and pullets in 2 other rooms were similarly infected at 19 weeks of age (at or near sexual maturity). Within 2 weeks after infection, internal organ samples were collected from the birds and tested to detect the presence of S. Enteritidis. The pathogen was found significantly more often in cage-reared pullets than in pullets reared in cage-free housing, especially when the birds were infected on the first day after transfer from the rearing facility. Also, the S. Enteritidis strain was recovered from internal organs more often when birds were infected at 19 weeks of age than at 16 weeks. These results suggest that pullet rearing conditions may have implications for the birds’ susceptibility to S. Enteritidis infection and reinforce the importance of attentive pathogen risk reduction practices when laying flocks are beginning to produce eggs. 3. Tissue colonization and egg and environmental contamination associated with the experimental infection of cage-free laying hens with Salmonella Braenderup. In 2018, a national recall of shell eggs in the United States occurred due to human illness caused by Salmonella Braenderup. Previous studies have detected Salmonella Braenderup in laying hens and the production environment, though little is known about the ability of this Salmonella serovar to infect laying hens and contaminate eggs. ARS researchers in Athens, Georgia, examined the invasiveness of the outbreak strain of Salmonella Braenderup in laying hens, as well as its ability to persist in the production environment. Recovery of Salmonella Braenderup was high in intestinal tissue samples. Salmonella Braenderup was recovered in a small number of eggshell and substrate composite samples. These results indicate that Salmonella Braenderup is not an invasive Salmonella serotype for cage-free laying hens, especially when compared to serotypes of concern to the egg industry. However, it may persist in the environment at low levels. 4. Environmental sampling method influence on detection of pathogens in cage-free aviary housing. Environmental sampling of layer housing systems is essential to identifying potential pathogens that are of concern to human health. In collaboration with Purdue University scientists, ARS researchers in Athens, Georgia, collected swabs to identify the natural occurrence of pathogens (Listeria, Campylobacter and Salmonella) at various locations in a cage-free aviary housing system. Environmental swabs were analyzed to detect the natural occurrence of the pathogens as well as duplicate swabs inoculated with a low dose Salmonella Enteritidis to determine the ability to detect lose doses in the presence of naturally occurring flora. Detection of Listeria was the highest at the beginning of the study (22 weeks of age) and decreased over time. Detection of Campylobacter was also the highest at this time, however the decrease through 39 weeks of age was more gradual. Interestingly, detection of Campylobacter was the greatest in concrete dust samples, which can be attributed to the presence of rodent excreta in the samples. Drag swabs and manure belt scraper swabs were the best sampling types for high detection of naturally occurring Listeria and Campylobacter. No naturally occurring Salmonella was identified in the study. The recovery of the Salmonella Enteritidis inoculum increased over time, with the highest rate of detection occurring just before United States mandatory Salmonella Enteritidis environmental monitoring at 40 – 45 weeks of age. Based on this study, the use of drag and manure belt scraper swabs are effective in detecting Listeria and Campylobacter in cage-free aviary housing. Along with good pest management, the occurrence of pathogens could be monitored and reduced in laying hen flocks. **Review Publications**
                            *Gast, R.K., Jones, D.R., Guraya, R., Garcia, J.S., Karcher, D.M. 2022. Internal organ colonization by Salmonella Enteritidis in experimentally infected layer pullets reared at different stocking densities in indoor cage-free housing. Poultry Science. https://doi.org/10.1016/j.psj.2022.102104.*
                                *Gast, R.K., Dittoe, D.K., Ricke, S.C. 2022. Salmonella in eggs and egg-laying chickens. Critical Reviews in Microbiology. https://doi.org/10.1080/1040841X.2022.2156772.*
                                *Garcia, J.S., Anderson, K.E., Guard, J.Y., Gast, R.K., Jones, D.R. 2023. Impact of paddock area stocking density of free-range laying hens on egg and environmental microbiology. Journal of Applied Poultry Research. https://doi.org/10.1016/j.japr.2023.100338.*
                                *Garcia, J.S., Jones, D.R., Gast, R.K., Karcher, D., Erasmus, M.A. 2023. Environmental sampling methods' influence on detection of pathogens in cage-free aviary housing. Poultry Science. https://doi.org/10.1016/j.psj.2022.102381.*
                                *Gast, R.K., Jones, D.R., Guraya, R., Garcia, J.S., Karcher, D.M. 2023. Internal organ colonization by salmonella enteritidis in experimentally infected layer pullets after rearing in conventional cage or cage-free housing. Journal of Applied Poultry Research. https://doi.org/10.1016/j.japr.2023.100334.*


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