Keel bone fractures affect a majority of commercial laying hens, causing chronic pain and reduced mobility — a major welfare problem discovered as systems transitioned away from battery cages.
Keel bone fractures represent a welfare challenge that was largely invisible in battery cage systems — where hens had no opportunity to fall from height — but became apparent as welfare-motivated transitions to cage-free systems revealed a new injury pattern. The welfare paradox of cage-free systems that allow normal behavior but introduce keel bone injury risk illustrates why welfare improvement must address specific mechanisms rather than just system type. Keel bone fractures cause ongoing pain that affects posture, movement, and behavior. Solving this problem requires genetic selection, improved aviary design that reduces fall height, and management practices that help hens land safely.