Internal organ colonization by salmonella enteritidis in experimentally infected layer pullets after rearing in conventional cage or cage-free housing

Authors: Gast, Richard; Jones, Deana; Guraya, Rupinder - Rupa; Garcia, Javier; KARCHER, DARRIN - Purdue University

Submitted to: Journal of Applied Poultry Research
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 1/10/2023
Publication Date: 3/1/2023
Citation: Gast, R.K., Jones, D.R., Guraya, R., Garcia, J.S., Karcher, D.M. 2023. Internal organ colonization by salmonella enteritidis in experimentally infected layer pullets after rearing in conventional cage or cage-free housing. Journal of Applied Poultry Research. https://doi.org/10.1016/j.japr.2023.100334.
DOI: https://doi.org/10.1016/j.japr.2023.100334

Interpretive Summary: Eggs contaminated by Salmonella Enteritidis are often implicated as sources of food-borne human illness because this pathogen can be deposited inside eggs after it invades to the internal organs of infected hens. The commercial egg industry is gradually implementing a transition from traditional cage-based housing to alternative systems to comply with animal welfare goals, but the food safety ramifications of this change remain incompletely understood. The present study assessed internal organ colonization and bird-to-bird (horizontal) transmission by S. Enteritidis in egg-type pullets reared in 2 different housing systems: conventional cages and cage-free floor pens. After rearing, pullets were moved at 16 wk of age to isolation rooms simulating commercial cage-free barns, with nest boxes, perches, and floors covered by wood shavings. One-third of the pullets in 2 rooms were orally infected with S. Enteritidis immediately after placement, and pullets in the other 2 rooms were similarly infected at 19 wk of age (at or near the point of sexual maturity). During the course of the first 2 wk after each introduction of infection, birds were euthanized and their internal organs were tested to detect the presence of S. Enteritidis. The pathogen was found significantly more often in cage-reared pullets than in pullets reared in cage-free housing, especially when the birds were infected on the first day after transfer from the rearing facility. Also, the S. Enteritidis strain was recovered from internal organs more often when the birds were infected at 19 wk of age than at 16 wk. These results reinforce the importance of attentive pathogen risk reduction practices at this critical phase in the productive life of egg-laying flocks.

Technical Abstract: Invasive Salmonella Enteritidis infection involving the reproductive organs of laying hens can result in the production of internally contaminated eggs, which continue to be prominent sources of disease transmission to consumers. The poultry housing environment exerts substantial influences on the dissemination and prevalence of S. Enteritidis in laying flocks, and the ongoing transition of the egg industry toward cage-free housing has raised new questions about the food safety ramifications. The present study assessed internal organ colonization by S. Enteritidis in egg-type pullets reared in 2 different housing systems (conventional cage and cage-free). At 16 wk of age, 4 groups of 72 pullets were moved into isolation rooms simulating commercial cage-free barns; 1/3 of the pullets in 2 rooms were orally inoculated with S. Enteritidis immediately after transfer and pullets in 2 rooms were similarly infected at 19 wk. At 6-12 d post-inoculation, all pullets were euthanized and samples of liver, spleen, and intestinal tract were removed for bacteriologic culturing. S. Enteritidis was isolated significantly (P < 0.05) more frequently from spleens and intestines from infected pullets that had been reared in cages than from those reared in cage-free housing, especially when the birds were infected on the day after transfer from the rearing facility. S. Enteritidis was also found significantly more often in livers from birds infected at 19 wk than at 16 wk. These results reinforce the importance of attentive pathogen risk reduction practices at this critical phase in the productive life of egg-laying flocks.