A global trend towards improving farm animal welfare has seen an increase in the use of alternative or cage-free housing systems, and several countries have implemented bans on caged egg production due to their barren nature. Individual states in the U.S. have also established cage-free regulations intending to improve hen welfare by providing more space and resources per hen than are possible in cages. Due to this legislative demand, along with pressure from corporate pledges to source only cage-free eggs within a short timeline, many egg producers are undergoing the costly transition to build, stock, and maintain cage-free production facilities. Hens housed in cage-free systems can move throughout their enclosures and can utilize resources like perches, litter areas, and designated nests. Unfortunately, the addition of these resources, along with increased freedom of movement for hens and interactions among conspecifics within the flock, have also had unintended consequences (including negative hen behaviors such as crowding/crushing one another and cannibalism, and hen behaviors that are undesirable to producers, like laying eggs outside of nest sites). Further, several space and resource guidelines are set on a per-hen basis and may not consider that certain hen behaviors require a varying amount of space, nor do they consider the potential influence of large portions of a flock behaving congruously (in both situations, the amount of space or resources allocated by guidelines may not be the actual amount that is used or needed by hens). As an additional consideration, many of hens' key behaviors are diurnal in nature and it is possible that synchronous flock movement to a certain resource at a certain time of day, coupled with management tactics used to curb undesired behaviors, could prevent hens from performing these behaviors based on their preferred temporal patterns. To better ensure that guidelines on cage-free husbandry and management practices actually improve hen welfare as intended, research should consider the influences of multiple factors on hen behavior. Therefore, the overarching℗ focus of this project was to examine how laying hens of different genetic strains perform dynamic and space-intensive behaviors in a multi-tiered aviary system. Behaviors chosen for examination were dust bathing and wing flapping, both of which have been deemed important by cage-free legislation. Commercial-style Natura60 aviaries were stocked with 4 genetic strains: Hy-Line Brown [HB], Bovan Brown [BB], DeKalb White [DW] and Hy-Line [W36]. In the first study, we found that white strains had higher rates of litter occupancy and more synchrony in dust bathing behavior compared to brown strains. White-feathered hens also had smaller interbird distances while performing a dust bathing bout, whereas hens of the brown strains had larger inter-bird distances and shortened the duration of dust bathing bouts in the presence of more hens on the litter or with less space between nearby hens. During initial placement in the aviaries, we saw a similar behavioral trend based on genetic strain: following a period of complete litter restriction, DW and W36 hens occupied litter in greater numbers and at a faster rate HB and BB hens. When doors to litter opened each day, hens not only gained access to litter but also to unfettered three-dimensional space. Hens of all 4 strains flapped their wings more in the first 85 minutes (11:35am-12:55pm) following doors' opening, suggesting their daily confinement within tiers may have influenced their motivation to wing flap once they had room to do so. While wing flapping, W36 hens required an average of 51.02 ℗ł 4.7 cm of vertical space; however, our hens were cage-reared and housed, and the manner in which they flapped may not be representative of hens with more muscle development and experience with wing flapping. The method we tested should be further utilized on dynamic behaviors on of hens from a variety of strains, ages, and backgrounds. Future work is needed to determine the space requirements of hens for particular resources rather than blanketed guidelines for space as a whole. Differences in social distancing, behavioral synchrony, and the time-of-day around specific resources need to be identified.
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