Applied Research Note: Internal organ colonization by Salmonella Enteritidis in experimentally infected layer pullets after rearing in conventional cage or cage-free housing

SUMMARY: 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; 24 pullets in each of 2 rooms were orally inoculated with S. Enteritidis immediately after transfer and 24 pullets in each of the other 2 rooms were similarly infected at 19 wk. At 6 to 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, especially among birds reared in cage-free housing. These results reinforce the importance of attentive pathogen risk reduction practices at this critical phase in the productive life of egg-laying flocks.