Keel Bone Fractures in Laying Hens: A Widespread Hidden Welfare Problem

Keel bone fractures affect the majority of laying hens in cage-free and enriched cage systems, causing chronic pain that is rarely detected and almost never treated.

Key Facts

Keel bone fractures affect an estimated 50-80% of laying hens in cage-free aviary systems and 30-60% in enriched colony cages — making them the most prevalent injury in commercial laying hens
The keel bone is the ridge of bone running along the sternum — hens use it as a landing point when jumping from perches, and impacts from poor landings cause fractures that range from hairline cracks to complete breaks
Most keel bone fractures go undetected during the life of the bird because hens do not show obvious pain behavior — the fractures are typically discovered only at post-mortem examination after slaughter
Research using pain scales and behavioral observation shows that hens with keel bone fractures show behavioral indicators of pain: reduced movement, altered perch use, and changes in social behavior consistent with chronic pain states
Risk factors for keel bone fractures include: poor perch design (slippery or too narrow), inadequate space between perch levels, inappropriate housing transitions, and possibly genetic predisposition in high-production breeds
Evidence-based interventions to reduce keel bone fractures include: perch design improvements, ramp provision to reduce jump height requirements, genetic selection for keel bone health, and gradual transition to perch use from early life
Keel bone fractures represent a significant welfare gap in cage-free systems — the housing is better than battery cages by multiple metrics, but a previously unrecognized welfare problem affects the majority of birds

Welfare Considerations

Keel bone fracture welfare is a case study in how transitioning to apparently better housing systems can reveal previously invisible welfare problems. Battery cages prevented keel bone fractures by preventing the perch-related falls that cause them — but the welfare deficit of battery cages was far larger than the welfare cost of keel bone fractures in cage-free systems. This does not argue for battery cages; it argues for continued improvement in cage-free system design to reduce keel bone fracture rates while maintaining the behavioral welfare advantages of cage-free housing. The welfare problem is particularly troubling because it is chronic and painful but invisible — hens with keel bone fractures do not obviously signal distress in ways that attract management attention. Developing practical on-farm detection methods and evidence-based prevention strategies is the current priority in laying hen welfare research.

What You Can Do

Support laying hen welfare research institutions working on keel bone fracture prevention through housing design and genetic approaches
Advocate for welfare certification standards that include keel bone fracture monitoring as a required metric in cage-free system assessment
Engage with egg retailers about keel bone fracture rates in their supply chains and what measures producers are taking to reduce prevalence
Reduce egg consumption overall and concentrate purchases on welfare-certified cage-free products from operations with documented keel bone monitoring
Share information about keel bone fractures with consumers who assume cage-free automatically means good welfare — the issue is more complex