Laying hens have strong instincts to perch at night, and denial of perching opportunities in cage systems causes frustration, while perching in furnished systems leads to widespread keel bone fractures.
Keel bone fractures represent a paradox in laying hen welfare: the systems designed to improve welfare by providing perches often cause painful injuries. Fractures occur when hens collide with perch edges or fall from heights. Chronic fractures impair movement, foraging, and normal social behavior. The problem is poorly monitored in commercial systems and rarely treated. Improving perch design, reducing perch height, and selecting for bone density through breeding are promising approaches, but implementation lags behind the scientific understanding of the problem.