Production systems for laying hens and broilers and risk of human pathogens

There is evidence that the type of production systems used for laying hens and broilers can affect the likelihood of the chickens being colonized by human pathogens. The most significant public health risk associated with layers is transmission of Salmonella to humans via eggs. Based on experimental and epidemiological data, however, it seems unlikely that the move from conventional cages to enriched cages and non-cage systems will result in an increase in the prevalence and/or shedding of Salmonella in laying hen flocks. Studies on broiler chickens suggest that free range and organic flocks are significantly more likely to be positive for Campylobacter at slaughter in comparison with first depopulated batches of conventionally reared broilers. Data in relation to broiler rearing system and the likelihood of birds being infected by other pathogens including Salmonella are scarce but there is no significant evidence to suggest that organic and free range broilers are more likely to be infected with Salmonella than are conventionally reared ones. There is some evidence for a higher level of antibiotic-resistant Campylobacter strains in conventional broilers compared with those found in organic ones and other antibioticresistant human pathogens are also more commonly isolated from conventionally reared broilers.