Motor ability and self-selection of an analgesic drug by fast-growing chickens

Breeding programs designed for broiler production have resulted in a chicken that, when fully fed, grows rapidly and has a body conformation that enhances yield at market weight. Compared with chickens bred for high egg production, the motor ability of broilers has been compromised and is of increasing concern in broiler breeding and production. Broilers with intermediate gait scores of 2, 3, and 4 were provided choices among diets containing different doses of a nonsteroidal anti-inflammatory drug (carprofen). Broilers with no identifiable gait abnormality (score of 1) or unable to walk (score of 5) were excluded from the study. The hypothesis that broilers with higher gait scores, if experiencing pain, would prefer diets with higher doses of carprofen was rejected because no differences were observed in feed consumption among treatment groups. Although males and females responded similarly, there was an interaction of sex with left-right preference for feeder location.