Fowl play: Do age and aviary design affect play in cage-free laying hens?

The laying hen industry in the United States is undergoing a transition toward cage-free housing systems, but the impact of specific layout designs on hen welfare remains poorly understood. Play behavior is widely recognized as a positive welfare indicator in mammals but has rarely been studied in birds. The goal of this study was to explore the effects of aviary design on play behavior in laying hens. We hypothesized that aviary design and age would significantly influence the frequency of play. A total of 2,464 Hy-Line Brown laying hens were randomly assigned at 16 weeks of age to two designs of multi-tiered aviary systems with litter area (N60 and STEP). Video recordings of the litter area were conducted on the first day of 17, 21, 27, and 32 weeks of age. After each play event, the number of birds in the litter area was recorded to estimate space per bird, and whether the behavior was triggered by play or flight of another bird in the same pen was noted. Running was most frequent at 17 weeks of age and declined sharply by 21 weeks, nearly disappearing thereafter, while frolicking and sparring showed similar early declines. In contrast, wing flapping decreased more gradually and remained present across all ages. The frequency of frolicking, running, wing flapping, and sparring declined significantly with age ( p < 0.0001). Aviary design significantly influenced the occurrence of running and wing flapping only ( p ≤ 0.0005), with running occurring more frequently in STEP and wing flapping more frequently in N60. In terms of the proportion of each play behavior relative to total play, significant age × design interactions were found for frolicking ( p = 0.0003), running ( p < 0.0001), and wing flapping ( p < 0.0001). Flying and play by other birds triggered over 50% of some behaviors, with play being the most common trigger. Play behaviors were most frequent in both designs when individual litter space ranged from 1,400–2,200 cm² per hen, while wing flapping peaked in N60 with 600–1,400 cm² per hen. Behavioral patterns were influenced by age in interaction with aviary design, emphasizing that the impact of housing layout may depend on the hens’ developmental stage. • Age reduced frequency of frolicking, running, sparring, and wing flapping • Aviary design influenced running and wing flapping but no other play types • Less running and more wing flapping seen in aviaries with one large litter area • Wing flapping emerged as the dominant play behavior toward the end of the study • Over 50% of play events were triggered by other hens’ playing or flying