Colonization of internal organs by Salmonella Enteritidis in experimentally infected laying hens housed in enriched colony cages at different stocking densities

Authors: Gast, Richard; Guraya, Rupinder - Rupa; Jones, Deana; ANDERSON, KENNETH - North Carolina State University; KARCHER, DARRIN - Michigan State University

Submitted to: Poultry Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 1/15/2016
Publication Date: 5/31/2016
Publication URL: https://handle.nal.usda.gov/10113/62810
Citation: Gast, R.K., Guraya, R., Jones, D.R., Anderson, K., Karcher, D.M. 2016. Colonization of internal organs by Salmonella Enteritidis in experimentally infected laying hens housed in enriched colony cages at different stocking densities. Poultry Science. 95:1363-1369.

Interpretive Summary: Most human illnesses caused by Salmonella Enteritidis have been attributed to the consumption of contaminated eggs. This bacterial pathogen is deposited inside the edible yolk or albumen of eggs when infection spreads to reproductive tissues of laying hens. Recently, alternatives to conventional caged housing for egg-laying flocks have been developed to address animal welfare concerns, but the food safety implications of poultry housing systems remain uncertain. The present study assessed some of the potential effects of housing laying hens in colony cages, enriched with perches and enclosed nesting areas, at two different two different stocking densities (defined by the amount of floor space available to each bird). Groups of hens were housed at two different stocking densities (and a third group was placed in conventional cages at the higher density). S. Enteritidis infection was initiated by oral inoculation and the birds were euthanized the following week so tissues samples could be collected and tested for colonization by the pathogen. S. Enteritidis was recovered more frequently from livers and ovaries of hens in enriched colony cages at the higher stocking density than at the lower density. However, S. Enteritidis was also recovered more often from spleens of hens in conventional cages than from those in enriched colony cages at the higher stocking density. These results demonstrate that stocking density can influence the susceptibility of hens to S. Enteritidis, but other characteristics of the various housing systems may also play important roles.

Technical Abstract: Epidemiologic analyses have linked the frequency of human infections with Salmonella enterica subspecies enterica serovar Enteritidis to the consumption of contaminated eggs and thus to the prevalence of this pathogen in commercial egg-laying flocks. Contamination of the edible contents of eggs by Salmonella Enteritidis is a consequence of the colonization of reproductive tissues in systemically infected hens. The animal welfare implications of laying hen housing systems have been widely debated, but no definitive consensus has yet emerged about the food safety significance of poultry housing options. The present study sought to determine the effects of two different bird stocking densities on the invasion of internal organs by Salmonella Enteritidis in groups of experimentally infected laying hens housed in colony cages enriched with perching and nesting areas. In two trials, groups of laying hens were distributed at two different stocking densities into colony cages enriched with perching and nesting areas and (along with a group housed in conventional cages) orally inoculated with doses of 1.0 × 107 cfu of Salmonella Enteritidis. At 5-6 d post-inoculation, hens were euthanized and samples of internal organs were removed for bacteriologic culturing. For both trials combined, Salmonella Enteritidis was recovered at a significantly (P < 0.05) greater frequency from hens in enriched colony cages at the higher stocking density than at the lower density from livers (75.0% vs. 51.4%) and ovaries (51.4% vs. 30.6%), However, spleens from hens in enriched colony cages at the higher stocking density were significantly less often positive for Salmonella Enteritidis than from hens in conventional cages at that same density (90.3% vs. 68.1%). These results suggest that stocking density can influence the susceptibility of hens to Salmonella Enteritidis, but other housing systems parameters may also contribute to the outcome of infections.