Colonization of internal organs by Salmonella Enteritidis in experimentally infected laying hens of four commercial genetic lines in conventional cages and enriched colony housing .

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

Submitted to: Poultry Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 11/2/2018
Publication Date: 4/1/2019
Citation: Gast, R.K., Regmi, P., Guraya, R., Jones, D.R., Anderson, K., Karcher, D.M. 2019. Colonization of internal organs by Salmonella Enteritidis in experimentally infected laying hens of four commercial genetic lines in conventional cages and enriched colony housing. Poultry Science. 98:1785-1790.

Interpretive Summary: Eggs contaminated with Salmonella Enteritidis can transmit disease to consumers, so the presence of this pathogen in commercial egg-laying flocks is an important public health concern. Eggs become contaminated when these bacteria reach the contents of eggs as they develop inside infected hens. In recent years, the type of housing used for laying hens has become a topic of considerable interest from the perspective of animal welfare, but the microbiological consequences of different systems remain unresolved. The present study evaluated the invasion of S. Enteritidis to internal organs of laying hens in two different housing systems. Laying hens from four commercial genetic lines (two that lay white eggs and two that lay brown eggs) were housed in either conventional cages or enriched colonies (which provide access to perches and nesting areas). All hens were experimentally infected with S. Enteritidis. Approximately one week later, internal organs were collected from infected hens and tested to detect S. Enteritidis invasion. S. Enteritidis was found more often in the intestinal tracts of hens from the two white egg lines than from the brown egg lines in either type of housing. For one brown egg line, S. Enteritidis was recovered from more intestinal samples of hens in conventional cages than from hens in enriched colonies. No differences between hen lines or housing systems were observed for any other internal organs. These results demonstrate that Salmonella Enteritidis colonization of the intestinal tract sometimes differs between genetic lines of egg-laying hens and that housing systems can influence Salmonella susceptibility for some lines.

Technical Abstract: The prevalence of Salmonella Enteritidis in commercial egg-laying flocks is a prominent public health concern because contaminated eggs cause human illness. Deposition of this pathogen inside eggs results from bacterial colonization of reproductive tissues in infected hens. Environmental conditions can influence avian Salmonella infections, but the food safety consequences of different poultry housing systems remain uncertain. The present study assessed the invasion of internal organs by Salmonella Enteritidis in groups of experimentally infected laying hens of four commercial genetic lines (designated as white egg lines W1 and W2 and brown egg lines B1 and B2). Groups of hens from each line were housed at 555 cm2 of floor space per bird in both conventional cages and colony units enriched with access to perches and nesting areas. All hens were orally inoculated with 5.75 × 107 cfu of a two-strain Salmonella Enteritidis mixture. At 6-7 d post-inoculation, hens were euthanized and samples of liver, spleen, ovary, oviduct, and intestinal tract were removed for bacteriologic culturing. The frequency of Salmonella Enteritidis recovery from intestinal samples was significantly (P < 0.05) greater for the two white egg lines combined than for the two brown egg lines combined in both conventional cage (72.2% vs. 50.0%) and enriched colony housing systems (66.7% vs. 37.5%). The frequency of intestinal Salmonella Enteritidis isolation from line B1 was significantly higher from hens in conventional cages (47.2%) than in enriched colonies (22.2%), but no differences were observed for other hen lines. Line W1 yielded more positive intestinal samples than either brown egg line in conventional cages, and Line B2 had fewer positive intestinal samples than all other lines in enriched colonies. There were no significant differences between hen lines or housing systems in Salmonella Enteritidis isolation from other internal organs. These results demonstrate that Salmonella Enteritidis colonization of the intestinal tract can vary between genetic lines of egg-laying hens and that some lines are subject to housing system influences on Salmonella susceptibility.