Location: Egg and Poultry Production Safety Research Unit
2025 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
Under Objective 1 effects of utilizing orange corn in laying hen poultry feed for enhanced yolk color on egg quality and functionality. A 1.5-year collaborative study between USDA-ARS researchers in Athens, Georgia; Purdue University; and Nutramaize, LLC has been completed to determine the impact of including orange corn in the diets of growing pullets and mature laying hens on egg production and quality. The laying flocks were managed at Purdue University and eggs were shipped to USDA-ARS for egg shape, physical quality (shell strength and deformation, albumen height, Haugh Unit score, vitelline membrane strength and deformation) and functionality assessments (emulsification capacity, noodle tensile strength, hard-cooked egg slicing and yolk color). USDA-ARS researchers are completing analysis of the data in preparation for publication of the results. This work was funded by a grant from USDA-NIFA-SBIR.
Under Objective 1 cage-free housing system design, hen use of resources, and egg microbial and physical quality. A collaborative study between USDA-ARS researchers in Athens, Georgia and Purdue University, was completed to compare how hens utilized available resources within differently designed styles of indoor cage-free housing systems, and how these different designs affected important microbiological parameters. Purdue University managed the laying flock and monitored egg production, egg efficiency, and hen well-being. USDA-ARS monitored Salmonella shedding during the rearing phase of the flock, then evaluated environmental microbiology (Salmonella), egg microbiology (Salmonella), and egg physical quality (shell strength and deformation, albumen height, Haugh Unit score, vitelline membrane strength and deformation, and whole egg solids) during the laying phase. ARS scientists are now analyzing data and preparing manuscripts for publication. The second phase of the project, the agent-based modeling phase, has begun and will generate a simulation for hen/system interactions based on data collected from the initial cage-free housing trials. This process will provide predictive information to guide management decisions for optimizing egg production while ensuring egg safety and quality. This work is funded by a grant from USDA-NIFA-IDEAS.
Under Objective 2 environmental contamination and horizontal transmission of Salmonella Enteritidis among egg-type pullets in a cage-free management system. A collaborative study between USDA-ARS researchers in Athens, Georgia and Purdue University was completed to evaluate environmental contamination and horizontal transmission of S. Enteritidis within groups of layer pullets in a cage-free system after infection just before the age of sexual maturity. The isolation of S. Enteritidis from diverse samples taken within the cage-free system environment during the first two weeks after the oral infection of different proportions of pullets was correlated with the frequency of recovery of the pathogen from the internal tissues of horizontally exposed birds.
Objective 2: Environmental contamination and horizontal transmission of Salmonella Enteritidis infection during conventional and in-place rearing of egg-type pullets in a cage-free management system. A collaborative study between USDA-ARS researchers in Athens, Georgia and Purdue University was begun to investigate the relationship between contamination of specific locations within a cage-free system and the horizontal transmission of infection in egg-type pullets experimentally infected with S. Enteritidis as young chicks or pullets and then either reared continuously in-place to between 16 and 17 weeks of age or subjected to a simulated transport experience at 14 weeks of age and then moved to clean facilities. Several types of sample types are being collected and tested from each room of birds at intervals during rearing.
Accomplishments
1. Environmental contamination and horizontal transmission of Salmonella Enteritidis among experimentally infected layer pullets in indoor cage-free housing. The bacterial pathogen Salmonella Enteritidis can cause human illness when it is deposited inside the edible interior contents of eggs laid by infected laying hens and the gradual transition of the commercial egg industry toward increased utilization of non-cage systems for hens raises new questions about the persistence and transmission of S. Enteritidis infections in flocks. ARS researchers in Athens, Georgia assessed S. Enteritidis contamination of the poultry housing environment and the horizontal transmission of infection within groups of immature laying hens (pullets) in a cage-free system. Groups of pullets in an isolation facility simulating a cage-free barn with perches and commercial kick-out nest boxes were orally infected with S. Enteritidis at different proportions (1/3, 1/6, or 1/12 of the birds). Five types of samples were collected from different locations in each room during the first 2 weeks post-infection, after which samples of several internal organs were collected from uninoculated birds (exposed to S. Enteritidis only by contact with inoculated pen-mates), and all samples were cultured to detect S. Enteritidis. The frequencies of recovery of S. Enteritidis from all types of samples were greatest when 1/3 of the birds were orally inoculated and were least when only 1/12 were inoculated. Wall dust and flooring substrate (pine shavings litter) composite samples provided high frequencies of recovery of S. Enteritidis, whereas drag swabs of the flooring substrate provided less effective recovery. These results suggest that a high frequency of environmental contamination may be an important contributor to the spread of S. Enteritidis infections among pullets in cage-free housing and demonstrated that the choice of environmental sampling methods can affect the recovery of S. Enteritidis.
2. Impact of egg handling and extended storage on egg quality. Eggs are important international agricultural commodities, but they are handled and stored differently around the world, including variations in practices for washing and refrigeration. USDA-ARS researchers in Athens, Georgia conducted a study that focused on the impact of egg handling and storage practices on egg physical quality. Conventional commercial white shell eggs were subjected to four different treatments: 1) unwashed, 2) washed, 3) washed and then sprayed with food-grade mineral oil, and 4) washed after being held under refrigeration for 21 days after collection. Eggs from each of these handling treatments were then stored either at refrigeration (4°C) or room temperature (22°C) and tested for several physical egg quality parameters over a period of 27 weeks. Egg quality (egg weight and albumen thickness) declined more rapidly during storage at room temperature than under refrigeration; high internal quality was maintained even in unwashed eggs for 27 weeks under refrigeration. Washing/oiling preserved quality longer during room temperature storage. These results, demonstrating the significance of storage temperature for preserving egg quality, are important for ensuring that domestic consumers receive high-quality eggs and for opening international markets to eggs produced according to US standards.