US - In two studies, researchers have found similar levels of Salmonella contamination on eggs from hens housed in conventional cages and colony cages after birds had been inoculated with the same dose of bacteria.
No significant differences were observed in the frequency of egg Salmonella contamination were observed between hens housed in conventional (battery) cages and colony cages (enriched cages), according to a study by Richard K. Gast of the USDA ARS Egg Safety and Quality Research Unit and other published in Poultry Science.
For both trials combined, Salmonella Enteritidis was recovered from 3.97 per cent of eggs laid by hens in conventional cages and 3.58 per cent of eggs laid by hens in enriched cages.
Both epidemiological analyses and active disease surveillance confirm an ongoing strong association between human salmonellosis and the prevalence of Salmonella enterica subspecies enterica serovar Enteritidis in commercial egg flocks, explained Gast and his co-authors in the paper. The majority of human illnesses caused by this pathogen are attributed to the consumption of contaminated eggs.
Animal welfare concerns have increasingly influenced commercial poultry production practices in recent years but the food safety implications of different housing systems for egg-laying hens are not definitively understood.
Their present study assessed the effects of two different housing systems (conventional cages and colony cages enriched with perching and nesting areas) on the frequency of Salmonella Enteritidis contamination inside eggs laid by experimentally infected laying hens.
In each of two trials, groups of laying hens housed in each cage system were orally inoculated with doses of 1.0 × 108 colony-forming units (cfu) of Salmonella Enteritidis. All eggs laid between five and 25 days post-inoculation were collected and cultured to detect internal contamination with Salmonella Enteritidis.
Gast R.K., R. Guraya, D.R. Jones and K.E. Anderson. 2014. Contamination of eggs by Salmonella Enteritidis in experimentally infected laying hens housed in conventional or enriched cages. Poultry Science. 93(3):728-733. doi: 10.3382/ps.2013-03641
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