Effects of bird age, density, and molt on behavioral profiles of two commercial layer strains in cages.

Two commercial strains, Hy-Line W-36 and DeKalb XL, were moved to a laying house at 18 wk of age. They were housed 6 hens/layer cage at 2 densities (361 and 482 cm2/bird) with 2 replications each per strain/density combination. The high-density treatment contained 24 hens/replication and the low-density treatment contained 18 hens/replication for a total of 168 hens. Production parameters were measured during the first egg production cycle, the molt period, and the first 4 wk of the second lay cycle (20 to 68 wk of age). Behavioral observations were taken during 2 consecutive d at 26, 34, 43, 51, 62, 64, and 68 wk of age to examine behavioral patterns. Modified Hansen's tests were conducted concurrently to provide indication of the fearfulness levels of hens at the various stages of production. The production characteristics were similar for both strains. The hens kept at the higher density had lower (P < 0.01) hen-day production and (P < 0.05) daily egg mass. Appetitive behaviors were not affected by strain or density but were affected by the age of the hen and by molting. During the molt, feeding and drinking behavioral acts were fewer (P < 0.05) at 0.018 and 0.013 acts per bird/min, respectively, and standing behavior was highest. The results indicated that the frequencies of pecking inedible objects during the molt period were similar to the frequencies at 26 and 34 wk. Hens performed more acts of standing, and crouching and had lower frequency of movement during the molt. Those kept at a low density performed more movement acts. Feather pecking decreased as hens aged and increased when they molted but was not affected by strain or density. The frequency of aggression and submissive acts was significantly lower during the molt period. Behaviors were affected by strain, density, bird age, and molting; however, the patterns and number of aggressive acts did not increase to compromise the welfare status of the hens. Behaviors during the molt appeared consistent with mechanisms for conservation of body reserves.