Abstract
Multi-tiered aviaries for laying hens are designed to provide resources, such as perches, that allow birds to perform natural behaviors, thus improving their welfare. This research examined nighttime roosting heights and substrates used by laying hens of 4 genetic strains (Dekalb White: W1, Hy-Line W36: W2, Hy-Line Brown: B1, Bovans Brown: B2), in multitier aviaries (144 hens/unit, 4 units/strain) at 25 to 28 wk of age (peak lay). Influence of litter provision on roosting patterns of the strains was also tested. Direct observations of hens' nighttime roosting patterns on wire floors, ledges and perches across tiers were conducted before (PRE), immediately after (IMM), and 3 wk after (ACC) hens gained access to litter. During all periods, more W1 and W2 hens roosted on middle and upper ledges than B1 and B2 hens (all P≤0.05), while more B1 and B2 hens used perches throughout the aviary than W1 and W2 hens (all P≤0.05). W1 (15±1.9, 14±3.36) and W2 (19±2.1, 18±2.6) hens occupied perches in the upper tier in greater numbers than B1 (7±3.2, 3±4.6) and B2 (11±2.1, 5±3.36) hens during PRE (P = 0.01) and ACC (P = 0.02) periods, respectively. B1 and B2 hens occupied wire floors in larger numbers than W1 and W2 hens during PRE (P = 0.02) and IMM (P = 0.03) periods, though this difference disappeared in the ACC period. During the IMM period, more W1 and W2 roosted in the lower tier, while more B1 and B2 hens were observed in the middle and upper tiers (all P ≤ 0.05). These findings demonstrate the importance of perches for B1 and B2 hens and space to roost higher in aviary units for W1 and W2 hens during the night, and underscore the need to consider aviary design, management practices, and preferences of different hen strains to ensure good hen welfare in aviaries.