January 19, 2009

A new study conducted in Sweden has discovered that free-range chickens are more vulnerable to disease than caged chickens.

Researchers at the National Veterinary Institute in Sweden noted that the number of dead chickens increased after switching the animals from battery cages to enriched cages and litter-based systems, including free-range.

The study found there were significantly more deaths in flocks farmed either free-range or from indoor litter-based systems than in flocks of caged chickens.

The most common cause of death was found to be bacterial infection, most often cuased by E. coli, which was more frequently seen in flocks from litter-based and free-range systems, according to the study.

Chickens from free-range and litter-based systems were also more likely to have been pecked by other birds, which can affect bird health and even lead to death. Parasitic infections caused by mites were also more common, but housing did not appear to affect the incidence of viral infections, said the study.

The researchers said experience and knowledge could help lower mortality and disease rates, and that measures can be taken to counter diseases.