Research note: Time of day and age affect hen activity patterns in two designs of cage-free aviaries

The laying hen industry is transitioning to cage-free housing, including multi-tiered aviaries, yet research on how aviary configuration influences movement is limited. We examined activity patterns in hens acclimating to two aviary designs. We hypothesized that hen age, time of day (TOD), and aviary design would influence activity. A total of 2,464 Hy-Line Brown hens were placed in two aviary designs (N60 and STEP) at 16 weeks of age (WOA), each replicated across two rooms with four pens per room. The two designs varied in litter accessibility and nest placement. At 18, 28, and 59 WOA, two focal hens per pen (n = 32/WOA) were fitted with triaxial accelerometers. Activity was analyzed for four one-hour periods on the recording day: 1 hour after lights on (morning), 1 hour during noon feeding (noon), 1 hour without management events (afternoon), and 1 hour before lights off (evening). A generalized linear mixed model was used to test the effects of design, age, and TOD, with room and individual hen included as random effects. Horizontal activity showed a significant age × TOD × design interaction (p < 0.0001). Evening consistently had the highest horizontal activity, while morning was typically lowest, except in specific age × design combinations. Vertical activity also showed a significant three-way interaction (p < 0.0001). Vertical activity peaked at 28 WOA across TOD and designs and was lowest at 18 WOA across most TOD in both designs. In summary, horizontal and vertical activity patterns were influenced by the combined effects of age, TOD, and aviary design. The significant three-way interactions indicate that these effects were context-dependent, with movement patterns shaped by the interplay of daily routines, housing design, and age of hens rather than any single factor alone.