Modern laying hens are selectively bred for high egg production, depositing calcium into eggshells at a rate that consistently exceeds dietary intake. This creates a chronic calcium deficit that is met by resorbing cortical bone, leading to severe osteoporosis by end of lay. Structural bone loss compromises skeletal integrity and increases fracture risk during handling and catching at slaughter.
The keel bone (sternum) is particularly vulnerable to fracture. Causes include collisions with perches, nest boxes, and other equipment; aggressive interactions; and the inherent fragility caused by osteoporosis. Fractures range from minor to severe and are associated with chronic pain, behavioural changes, and reduced welfare. Many hens live with untreated fractures for weeks or months.
Keel bone fractures can be detected by palpation during welfare assessments. Fractures are scored as palpable deviations (deviations without fracture), old callus fractures (healed), or fresh fractures (acute). Regular on-farm assessment allows monitoring of flock-level prevalence and intervention effectiveness.
Keel bone fractures are now a research priority for egg industry welfare. The Bristol study (Wilkins et al.) and subsequent work has established prevalence data across EU systems. Policy developments in the UK and EU increasingly require producers to monitor and report keel bone health as part of welfare assurance schemes.