title: Colonization of internal organs by Salmonella Enteritidis in experimentally infected laying hens housed in enriched colony cages at different stocking densities.
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 and (along with a group housed in conventional cages) orally inoculated with doses of 1.0 × 10(7) cfu of Salmonella Enteritidis. At 5 to 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.
authors.affiliation: USDA Agricultural Research Service, U. S. National Poultry Research Center, Athens, Georgia 30605 Richard.Gast@ars.usda.gov.
authors.forename: Richard K
authors.initials: RK
authors.lastname: Gast
authors.affiliation: USDA Agricultural Research Service, U. S. National Poultry Research Center, Athens, Georgia 30605.
authors.forename: Rupa
authors.initials: R
authors.lastname: Guraya
authors.affiliation: USDA Agricultural Research Service, U. S. National Poultry Research Center, Athens, Georgia 30605.
authors.forename: Deana R
authors.initials: DR
authors.lastname: Jones
authors.affiliation: Department of Poultry Science, North Carolina State University, Raleigh, NC 29765.
authors.forename: Kenneth E
authors.initials: KE
authors.lastname: Anderson
authors.affiliation: Department of Animal Science, Michigan State University, East Lansing, MI 48824.
authors.forename: Darrin M
authors.initials: DM
authors.lastname: Karcher
mesh_terms: D000818:Animals; D002645:Chickens; D005260:Female; D006799:Housing, Animal; D011156:Population Density; D011201:Poultry Diseases / Q000382:microbiology*; D012481:Salmonella Infections, Animal / Q000382:microbiology*; D012477:Salmonella enteritidis / Q000502:physiology*
keywords: Salmonella Enteritidis; conventional cages; enriched colony cages; laying hens; stocking density