Perch Positioning Affects both Laying Hen Locomotion and Forces Experienced at the Keel

Simple Summary Keel bone fractures in laying hens can occur due to falls and collisions within the housing system, although other factors such as genetics and nutrition contribute to the high fracture prevalence found in commercial laying hens. In addition, routine behaviors such as dustbathing or locomotion might contribute to the problem due to accumulated forces at the keel. To understand how locomotion affects the risk to sustain a fracture, we trained 20 brown and 20 white laying hens to jump from a platform to a perch installed at different angles, distances, and directions. We found that longer distances and steeper angles-especially during downward transitions-resulted in higher force at the keel and were more difficult for the hens to navigate. Our results show that perch position has an impact on the forces which a keel bone needs to absorb during controlled movements. In addition, perch position affects the hens' ability to move safely from perch to perch, i.e., without falls and collisions. Optimizing perch position could help to create a safer environment for laying hens and might reduce keel bone fractures. The aim of this study was to assess the effect of perch positioning on laying hens' locomotion and the resulting energy experienced at the keel. Twenty Nick Chick and 20 Brown Nick hens were trained to transition from a platform to a perch in several configurations. Three variables of perch positioning were tested in a 2 x 2 x 2 factorial design: direction (upward vs. downward), angle (flat vs. steep), and distance (50 cm vs. 100 cm). All hens were tested for five jumps of each treatment combination at 27-28 weeks of age. As predicted, we found steep angles and long distances to result in higher peak forces and impulse during take-off, flight, and landing; longer latency to jump; a higher likelihood to perform balancing movements; and a longer latency to peck at the provided food reward. The effect of perch positioning on locomotion and force at the keel during downwards jumps and flight was more pronounced in Brown Nick hens than in Nick Chick hens. Although we cannot state how the observed forces at the keel relate to the risk for keel bone fractures, our results indicated that optimizing perch positioning can reduce accumulated forced at the keel and consequent risk for fracture due to unsuccessful transitions.