Keel bone fractures are one of the most common and underappreciated welfare problems in laying hens. They affect the majority of hens in free-range and cage-free systems and cause chronic pain.
Keel bone fractures represent a welfare paradox in cage-free egg production: systems designed to improve welfare have unexpectedly high rates of this painful condition. Hens with fractured keels show reduced activity, altered posture, and analgesic-seeking behaviour consistent with chronic pain. The fractures result from collision with perches, ramps, and enclosure walls during flight and landing. Improved enclosure design, perch configuration, and selective breeding for bone strength are active research areas.