Abstract
Domestic chickens kept for egg laying navigate inclines such as ramps in some commercial housing systems to aid in transitions between housing tiers. Laying hens use their wings and hindlimbs in a locomotion called wing-assisted incline running (WAIR) to ascend steep inclines. There is a potential relationship between the strength of the main flight muscles and the health of the keel bone from which they originate. We sought to test the effects of a controlled, WAIR-based exercise regimen during rearing on keel bone health and muscle properties of white- and brown-feathered laying hens. The WAIR exercise regimen, which consisted of exercise twice weekly for 16 weeks did not promote increases in muscle mass or physiological cross-sectional area at 21 weeks of age (WOA) and did not provide long-term benefits on keel fracture prevalence at 40 WOA. However, the brown-feathered birds were found to have lower amounts of keel fractures at 40 WOA in comparison with the white-feathered birds. Future studies should test for training that begins before chicks become fully feathered, exercises that emphasize full excursion of the wing during downstroke and different levels of intensity, frequency and duration to optimize flight muscle architecture and promote keel bone health.