Effect of alternating lights and strain on behavior and leg disorders of roaster chickens.

The effects of light treatment and strain on movement, spacial distribution, activity, and incidence of leg disorders of 4 to 10-week-old male chickens were examined in two experiments. In both, an alternating light treatment, in which high-intensity light alternated from one side of the barn to the other against a background of low intensity light, was compared with a control light treatment of continuous low intensity light supplied to both sides of the barn. Two strains were tested in each experiment. In Experiment 1, chickens responded to the alternating light between 4 and 7 weeks of age, although not between 7 and 10 weeks of age, by moving into areas of relatively high intensity light. In Experiment 2, chickens responded during both periods by moving into areas of relatively low intensity light. Bird distribution was also affected by a geographical side preference. In both experiments, activity was higher in areas of high vs. low light intensity, higher under alternating than control light, and higher for younger than older birds (P less than .05). Activity was also influenced by strain (P less than .01). Incidence of leg disorders was influenced by strain (P less than .01) but not light treatment.