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United States Department of Agriculture

Agricultural Research Service

Related Topics

Research Project: Microbiological and Product Quality Consequences of Housing Laying Hens in Production Systems

Location: Egg Safety and Quality

2011 Annual Report


1a.Objectives (from AD-416)
Develop processing and storage options for small flock egg producers to ensure egg safety and quality. Evaluate the role of various production and management systems on the detection, transmission, and persistence of Salmonella spp. in eggs and the surrounding production environment (e.g. flocks and house contamination). Evaluate the role of various production and management systems on the immune parameters of chickens and whether the immune responses can be used as an intervention approach. In conjuction, this project will evaluate the immune response as a potential marker of pathogen load or as a marker for critical points for interventions.


1b.Approach (from AD-416)
Egg safety and quality issues often initiate in production and storage before entering the processing facility. There is a need for a farm-to-fork approach to product safety and quality, especially in light of new federal regulations and increased interest in alternative housing systems to replace housing hens in cages. Research will serve today’s fully integrated and streamlined egg industry most effectively if it covers the full scope of egg production to processing. Additionally, strategies to assist small flock egg producers enhance product safety and quality will also be developed. These goals will be accomplished by assessing the role of production systems on naturally occurring flora and pathogens in and on shell eggs, evaluating the effects of federally mandated storage conditions on the microbial and physical quality of eggs from various production systems, and developing processing and storage options for small flock egg producers to ensure egg safety and quality. The poultry house environment plays a highly significant role in Salmonella infections of laying flocks. This research will determine how different production systems for housing laying hens affect the transmission and persistence of experimentally introduced Salmonella infection or house contamination and the associated frequency and nature of egg contamination. It will also determine how different production systems affect the detection of Salmonella in laying flocks and their housing environment, and evaluate the performance of testing methodologies for detecting S. Enteritidis and other Salmonella spp. in flocks and eggs from different production systems to develop rapid, sensitive, and cost-effective testing strategies. Eliciting a strong immune response against Salmonella spp. is crucial for preventing or reducing flock infections and ultimately Salmonella-contaminated eggs. Stress caused by raising hens in different production systems could compromise the response and exacerbate the Salmonella problem. This research will focus on the development of systemic and mucosal immunity by hens housed under different production conditions in response to infection or vaccination. Information regarding the strengths and weaknesses of the different systems with regards to development of Salmonella immunity will be determined enabling industry to design effective production facilities which address both the welfare and immunocompetence of the hens.


3.Progress Report
Presence of naturally occurring flora and pathogens in and on shell eggs from various production systems. Commercial-based research flocks (single genetic strain and multiple genetic strain studies) in various alternative production systems were monitored for 15 months. Data analysis is currently underway to determine what differences in aerobic, Enterobacteriaceae, and yeast and mold populations exist. Listeria and Campylobacter prevalence were also monitored.

Testing to detect Salmonella in environmental and egg samples from laying hens housed in several simulated commercial housing systems. Among 12 sets of egg and environmental samples obtained over a 15-month period from flocks of laying hens held in several different housing systems at research facilities of North Carolina State University, none of 147 environmental samples and 91 pooled egg contents samples were Salmonella-positive, but 4 of 220 crushed egg shell samples were positive for serogroup B Salmonella.

Frequency and magnitude of internal organ colonization following exposure of laying hens to different oral doses of Salmonella (S) Enteritidis. An experimental infection study determined that the number of S. Enteritidis cells found in the livers of infected hens at two different intervals after oral inoculation was significantly greater for the largest exposure dose administered than for either of two smaller doses.

Development of a disease-containment facility for studying the effects of housing systems on Salmonella Enteritidis infections in egg-laying hens. To accommodate experimental infection studies conducted under stringent disease-containment conditions, planning was initiated for the conversion of a facility containing single-bird research cages into a more accurate simulation of several commercially relevant housing systems.

Comparing egg quality from hens housed in various commercial production systems. A study is currently underway comparing conventional and enriched cage, as well as aviary production systems in commercial egg production. Monthly, eggs are monitored for shell and egg component physical quality attributes. Quarterly, a sample of eggs are washed and refrigerated to determine the rate of egg quality decline over 12 weeks.

Changes in egg quality as a result of in-shell egg pasteurization. Both an in-plant and extended storage study were conducted to quantify changes in egg physical quality. The in-plant study found no differences in vitelline membrane strength between control and pasteurized eggs. Pasteurized eggs had greater shell dynamic stiffness. A 12 week refrigerated storage study has also been completed and data are currently being analyzed. The storage study was more extensive and monitored shell and egg component physical properties.

This project replaces a portion of 6612-41420-014-00D Egg Processing Safety, Quality and Security and all of 6612-32000-003-00D Stress Effects on Immunity and Physiology of Poultry.


4.Accomplishments
1. Frequency and magnitude of internal organ colonization following exposure of laying hens to different oral doses of Salmonella (S) Enteritidis. ARS researchers in Athens, Georgia determined that the number of S. Enteritidis cells found in the livers of infected hens at two different intervals after oral inoculation was significantly greater for the largest exposure dose administered than for either of two smaller doses. Although eggs contaminated with S. Enteritidis continue to pose a significant public health concern, many important aspects of S. Enteritidis infections in egg-laying hens which affect the ability to accurately detect infected flocks remain unresolved. The present study evaluated one such parameter - the relationship between the oral dose of bacterial cells to which hens are exposed and the numbers of bacteria that reach the internal tissues of infected birds - by experimentally infecting groups of laying hens with several different oral doses of S. Enteritidis (ranging from 104 to 108 cells) and determining S. Enteritidis levels in the livers of infected hens 5 days and 20 days later. These results demonstrate that the oral exposure dose significantly affects important parameters of S. Enteritidis infection in laying hens which could influence the sensitivity of detecting different levels of exposure to this pathogen using particular sampling and testing methods. The egg industry can utilize these results to better develop S. Enteritidis testing schemes in production flocks.


Review Publications
Gast, R.K., Guraya, R., Guard, J.Y., Holt, P.S. 2011. Frequency and magnitude of internal organ colonization following exposure of laying hens to different oral doses of Salmonella Enteritidis. International Journal of Poultry Science. 10:325-331.

Last Modified: 11/20/2014
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