Egg-laying hens suffer from osteoporosis at epidemic rates due to the calcium demands of intensive egg production. Bone fractures — during life and at slaughter — represent a major welfare burden.
Laying hen bone disease is one of the most prevalent and underappreciated welfare problems in commercial egg production. The relentless calcium demand of producing an egg every 25 hours depletes skeletal calcium faster than dietary intake can replace it, producing a progressive osteoporosis that weakens bones throughout the hen's productive life. Keel bone fractures — painful breaks of the large breastbone — are so prevalent in some cage-free aviaries that they represent a near-universal welfare harm in non-cage systems. The fractures occur from collisions with perches and housing equipment in enriched environments, creating a perverse situation where systems intended to improve welfare create new welfare problems. Solutions require both improved housing design to reduce fall and collision injuries and research into management practices that reduce fracture incidence without returning to caged systems.