A white free range chicken.

Higher mortality in free-range poultry systems not only affects bird welfare but may also increase environmental impacts, according to a summary report from the Council for Agricultural Science and Technology (CAST).

CAST, a network whose membership includes many of the major U.S. professional societies in agriculture, reviewed dozens of studies that focused on free-range production in both layers and meat birds.  Many of the findings will be familiar to egg farmers and the paper summarizes the current state of knowledge rather than breaking new ground.

CAST says that while consumers may perceive free-range systems to be “more animal welfare friendly,” the actual research comparing different production systems “is inconclusive and often contradictory.”  The report finds some nutritional differences between eggs from pastured and caged hens, but says the differences are “related to their diet and not whether or not the hens were outside.”

On food safety, CAST reports that study findings are contradictory on which housing system holds the greatest risk of Salmonella infection.  It notes that pesticide, heavy metal and lead residues may be more of a concern in free-range flocks because of their direct contact with the soil.

For both layers and meat birds, CAST cited studies that would surprise many consumers.  Less intensive systems like free-range production tend to require more feed and land to produce a given amount of eggs or meat and their environmental impact may be greater than that of conventional production.  The complete CAST paper is available here.