Submitted to: Poultry Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: January 30, 2013
Publication Date: February 1, 2013
Citation: Gast, R.K., Guraya, R., Jones, D.R., Anderson, K.E. 2013. Colonization of internal organs by Salmonella Enteritidis in experimentally infected laying hens housed in conventional or enriched cages. Poultry Science. 92:468-473. Interpretive Summary: The majority of human illnesses caused by Salmonella Enteritidis have been linked to the consumption of contaminated eggs. This pathogen is deposited in the edible internal contents of eggs when infections of laying hens spread to internal tissues, including the reproductive organs (ovary and oviduct) where eggs are formed. In recent years, the consequences of different types of housing systems used for laying flocks have been widely discussed around the world in regard to their significance for both animal welfare and food safety. In the present study, two different types of housing (conventional and enriched cages) were evaluated for their effects on internal organ colonization in laying hens infected with S. Enteritidis. Enriched cages are colony-type units providing greater floor space per bird with perches, enclosed nesting areas, and scratching surfaces. After groups of laying hens were housed in each cage system and infected by oral inoculation, samples of internal organs were later removed from euthanized birds and tested for S. Enteritidis colonization. Although no difference between the housing systems was seen for colonization of the intestinal tract, S. Enteritidis was found at a significantly higher frequency in liver, spleen, ovary, and oviduct samples from hens in conventional cages than from hens in enriched cages. These results demonstrate that differences in housing systems for egg-laying flocks can affect the susceptibility of hens to infection and internal organ colonization by S. Enteritidis.
Technical Abstract: More human illnesses caused by Salmonella Enteritidis throughout the world have been linked to the consumption of contaminated eggs than to any other food vehicle. Deposition of this pathogen in the edible contents of eggs occurs when systemic infections of laying hens involve colonization of reproductive organs. In recent years, the consequences of different housing systems for laying flocks have become the focus of international attention from both animal welfare and public health perspectives. Nevertheless, many questions remain unresolved regarding the food safety implications of various laying hen production systems. The present study assessed the effects of two different housing types (conventional and enriched cages) on the invasion of internal organs by S. Enteritidis in experimentally infected laying hens. In two trials, groups of laying hens housed in each cage system were orally inoculated with doses of 1.0 × 107 cfu of S. Enteritidis. At 5-6 days post-inoculation, hens were euthanized and samples of internal organs were removed for bacteriologic culturing. For both trials combined, S. Enteritidis was recovered from 95.3% of cecal samples, with no significant differences observed between housing systems. However, S. Enteritidis was detected at significantly (P < 0.05) higher frequencies from hens in conventional cages than from hens in enriched cages for samples of livers (96.9% vs. 75.0%), spleens (93.8% vs. 53.1%), ovaries (25.0% vs. 10.4%), and oviducts (19.8% vs. 2.1%). These results demonstrate that differences in housing systems for egg-laying flocks can affect the susceptibility of hens to colonization of internal organs by S. Enteritidis.