Laying Hen Mortality and Smothering: Welfare Failures in Cage-Free Systems

Smothering and piling deaths are significant welfare problems in cage-free aviary systems. Understanding their causes enables management interventions that save lives.

Key Facts

Smothering occurs when hens pile on top of each other, typically at dusk when returning to perch — those on the bottom suffocate
Smothering mortality can reach 0.5-1% of the flock in poorly managed aviary systems
Causes include insufficient perch space, lighting transitions that panic birds, and unfamiliar aviary layouts
Light management (dimming lights gradually at dusk) significantly reduces panicked piling behaviour
Training hens to use perches from a young age reduces adult piling
Well-managed cage-free systems with good light management and adequate perch space have very low smothering rates

Welfare Considerations

Smothering deaths cause significant welfare harm — birds crushed beneath panicking flock members face hypoxia and physical compression before death. That these deaths are largely preventable through management makes them particularly significant welfare failures. Light management at dusk, training pullets to use perches before placement in laying systems, providing adequate perch space, and ensuring appropriate aviary layout reduce smothering to very low levels in well-managed systems. The welfare of cage-free hens cannot be assumed from the housing system alone — management quality determines actual welfare outcomes. Regular monitoring of mortality causes provides the data needed to intervene appropriately.

What You Can Do

Advocate for cage-free welfare standards to include smothering mortality monitoring and reporting
Support farm assurance schemes that audit management practices known to reduce smothering risk
Engage egg producers and retailers about smothering prevention as a specific welfare outcome measure
Support research into lighting protocols and pullet training that minimise smothering risk
Choose eggs from farms with publicly reported welfare outcome data including mortality causes