Multi-Tier Aviary Systems for Laying Hens

Multi-tier aviary systems represent a significant improvement over conventional cages for laying hens, allowing expression of natural behaviours while presenting new management challenges for welfare.

Key Facts

Multi-tier aviaries allow hens to fly, perch, dustbathe, and lay in nest boxes
They can house more birds per floor area than single-level cage-free barns
Keel bone fractures remain a welfare concern as hens navigate between tiers
Ammonia levels require careful ventilation management in densely stocked aviaries
Hens in well-managed aviaries show lower rates of fear responses than caged counterparts
Mortality can be higher in early life if chicks are not trained to use all tiers
Research shows that hens use the full vertical space, indicating genuine preference for height

Welfare Considerations

Multi-tier aviaries represent a meaningful welfare advance over enriched cages by allowing hens to engage in the full range of natural behaviours including flying, perching at height, and dustbathing. However, transitioning between tiers causes a high rate of keel bone fractures — injuries that cause chronic pain and affect up to 80% of hens in some studies. Ramp design, lighting gradients to guide movement, and early training of pullets to use system features all influence fracture rates. Air quality in poorly managed aviaries can cause respiratory disease. The welfare promise of cage-free is most fully realised when management standards match system design.

What You Can Do

Choose eggs labelled as coming from well-managed cage-free aviary systems
Support retailers that require third-party welfare auditing of aviary-housed hen suppliers
Advocate for industry investment in keel bone fracture research and prevention
Encourage farm assurance bodies to include keel bone fracture rates in their scoring
Learn to distinguish between different cage-free systems when reading food labels