IntroductionTo prepare laying hens for life in cage-free aviaries, they must be reared in aviaries that accustom them to the challenges of navigating a complex three-dimensional structure. Rearing aviaries vary in design and contain a brooding compartment in which chicks are confined during the first six weeks of age. These compartments vary greatly in their size and complexity. The present study aimed to examine the impact of environmental complexity during early life and birds’ genetic strain on their space use and forms/types of exercise.MethodsFour consecutive flocks of brown and white chicks were raised in three styles of rearing aviary with low, intermediate, or high complexity. Behavioral observations were performed at three ages during the brooding phase (weeks 1, 3, and 5) and the open phase when the brooding compartments were opened (weeks 7, 11, and 17). Behaviors observed were categorized as aerial locomotion, perching, dynamic load-bearing behavior (DLB), and wing-involved load-bearing behavior (WLB).ResultsDuring the brooding phase, chicks in aviaries of high complexity exercised most frequently (e.g., DLB events/minute: 1.75 in High vs 1.11 in Mid and 0.10 in Low, p<0.0001), and the effect remained for whites, but not the browns, during the open phase. White pullets exercised more than brown pullets both in brooding (e.g., 1.47 vs 1.28 DLB events/minute, p<0.0001) and open phases in High and Mid (e.g., 1.17 vs 0.93 DLB events/minute, housing x stain interaction p=0.009). Throughout rearing, whites had higher odds of perching than browns (brooding: 0.52 vs 0.45, p=0.04, open: 0.27 vs 0.17, p=0.0007).DiscussionWe concluded that rearing aviary design can affect behavior during the brooding phase; however, once the brooding compartments were opened, housing differences almost exclusively affected white pullets. The data suggest that genetic strain of birds must be considered in the design of pullet housing with the goal of maximizing space use and musculoskeletal development of laying hen pullets.

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Adult laying hens are increasingly housed in spatially complex systems, e.g., non-cage aviaries, where locomotion between elevated structures can be challenging for these gallinaceous birds. This study assessed the effect of early environmental complexity on spatial skills in two genetic strains. Brown (B) and white (W) feathered birds were raised in: Conventional cages with minimal complexity (Con) or rearing aviaries with low (Low), intermediate (Mid), or high complexity (High). Birds from each housing treatment were challenged at three different time points in three different, age-appropriate vertical spatial tasks. Whites performed better than brown birds in all tests regardless of rearing environment. In chicks, test performance was predominantly explained by variation between replicates and differences in motivation for test participation. Treatment effects were seen in pubertal birds (pullets), with pullets from aviaries performing better than those from Conv. White High pullets performed better than white Mid or Low, an effect that was not found in browns. Pullets preferred to use a ramp to move downwards, but only when ramps had previously been experienced and when the ramp was not too steep. Overall, early environmental complexity affected spatial skills of laying hen pullets with stronger effects in white than brown feathered birds.

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