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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** 2022 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 experimentally infected layer pullets reared at different stocking densities in indoor cage-free housing. A study was completed to assess horizontal transmission and invasion of internal organs by S. Enteritidis in pullets reared at two different stocking densities in cage-free housing and experimentally infected at either 16 or 19 weeks of age. Susceptibility to S. Enteritidis was not significantly affected by pullet stocking density but was increased when birds were infected near the age of sexual maturity.  

Internal organ colonization by Salmonella Enteritidis in experimentally infected layer pullets reared in conventional cage or cage-free housing. A study was completed to assess horizontal transmission and invasion of internal organs by S. Enteritidis in pullets in cage-free housing, experimentally infected at 16 or 19 weeks of age after rearing in either conventional cage or cage-free housing. Significantly greater susceptibility to S. Enteritidis infection was observed after pullets were reared in conventional cage housing.

Hand hygiene during handling of shell eggs. Shell eggs are a raw agricultural commodity and are assessed for egg quality after processing via hand candling. Hand candling requires a training grader to utilize sight and feel for assessing the egg. A study was conducted to determine the general microbial impact of three methods of hand hygiene: washing hands with soap and water; utilizing ethanol-based hand sanitizer; or wearing nitrile gloves. Hands or gloves were swabbed immediately after hygiene practices were conducted and then again after graders had collected and assessed five 100 egg lots. Five replicates of each treatment were conducted in 3 different egg processing facilities. There were no differences in total aerobic organisms swabbed from hands or gloves after 5 grading lots were assessed.

Impact of hen genetics on egg shape and functional characteristics. A study is underway 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. The results of this study will aid in understanding if differences exist for egg functionality between strains of laying hens. 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 three 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 during the rearing phase of the flock. As the flock progresses in age, environmental and egg microbiology, as well as egg physical quality will also be 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 is underway 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 is monitoring environmental and egg microbiology for indicator populations of total aerobes and coliforms, as well as detection of Salmonella and Campylobacter spp. This study is funded, in part, through a collaborate grant from the Egg Industry Center.

Instrument enhanced egg grading. In collaboration with USDA AMS and Purdue University, the team is working with egg processing equipment manufacturers to determine if controlling check detection sensitivity settings on egg processing equipment can allow for alternate egg sampling rates while maintaining USDA grade integrity. This work is being undertaken to understand if sampling rate can be altered, reducing costs to egg producers and relieving some of the staffing pressures for USDA AMS in official shell egg plants. This research is being funded in part by USDA AMS through an agreement with Purdue University.

Egg sampling rate assessment and modeling. In collaboration with USDA AMS and Purdue University, the team is utilizing 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 will be conducting a second phase trial of alternate sampling rate fall 2022. USDA ARS will oversee 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. Since being made available, over 9,000 views have occurred. Due to industry enthusiasm and feedback, the modules are currently being translated and recorded in Spanish. **Accomplishments**
                                

1. Contamination of eggs by Salmonella Enteritidis and Salmonella Typhimurium in experimentally infected laying hens in indoor cage-free housing. Eggs contaminated with Salmonella can pose a risk to public health, but the food safety consequences associated with the various housing systems used in commercial egg production have not been fully resolved. ARS researchers in Athens, Georgia, assessed the frequency of internal contamination of eggs with Salmonella following experimental inoculation of a small proportion of laying hens housed on wood shavings in isolation rooms simulating commercial cage-free barns with nest boxes and perches. The frequencies of contamination in eggs laid in nest boxes or on the floors were similar, but more contaminated eggs were found after infection with S. Enteritidis than with S. Typhimurium. These results demonstrated that infection of a relatively small proportion of hens in cage-free housing with invasive Salmonella strains can lead to egg contamination over a period of nearly a month after exposure, especially for the epidemiologically important serovar S. Enteritidis. 2. Impact of extended egg storage conditions on egg microbial and physical quality factors. ARS scientists in Athens, Georgia, completed a six-month study to determine the impact of egg handling practices (washed, washed and oiled, stored 21 days then washed, and unwashed) and egg storage conditions (refrigerated and room temperature) on the microbial and physical quality of shell eggs. Refrigeration has a greater impact on the microbial and physical quality of eggs than egg handling practices. For the first time, typical egg handling practices utilized throughout the world were compared over a prolonged period of egg storage at both refrigerated and room temperatures. Therefore, the results provide a complete and direct comparison of egg handling and storage practices which can be utilized internationally when assessing egg import and export standards. **Review Publications**
                            *Gast, R.K., Jones, D.R., Guraya, R., Anderson, K.E., Karcher, D.M. 2021. Contamination of eggs by Salmonella Enteritidis and Salmonella Typhimurium in experimentally infected laying hens in indoor cage-free housing. Poultry Science. 100(11). https://doi.org/10.1016/j.psj.2021.101438.*
                                *Garcia, J.S., Jones, D.R., Gast, R.K., Robison, C.I., Regmi, P., Karcher, D.M. 2022. Influence of forage substrates on environmental and egg microbiology in cage-free aviary housing flocks. Journal of Applied Poultry Research. https://doi.org/10.1016/j.japr.2021.100225*
                                *Garcia, J.S., Gast, R.K., Guard, J.Y., Karcher, D.M., Jones, D.R. 2022. Tissue colonization and egg and environmental contamination associated with the experimental infection of cage-free laying hens with Salmonella Braenderup. Avian Diseases. 66:74-78.*


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