Keel bone fractures affect the majority of laying hens in many systems and cause chronic pain, representing one of the most significant welfare problems in egg production.
Keel bone fractures in laying hens represent one of the most widespread but underrecognised welfare problems in animal agriculture. The keel bone — a large ventral extension of the sternum — is fractured in a majority of hens in most commercial systems, typically during collisions in aviary and free-range housing. Fractures cause chronic pain detectable through behavioural indicators and response to pain relief. The problem is not resolved by higher-welfare systems alone — fracture rates in enriched and free-range systems, while lower than in cages, remain substantial. Genetic selection for bone strength, housing design improvements, and the development of better perch systems are active areas of welfare research.