Dust bathing is a fundamental behavioral need for laying hens that cannot be met in cage systems and is insufficiently provided in many cage-free systems.
Dust bathing motivation is so strong in hens that they perform sham dust bathing on wire floors without substrate — a behavioral indicator of frustration. The behavior is controlled by internal motivation cycles independent of soiling level. Adequate litter quality and quantity for dust bathing is a welfare requirement, not an optional enrichment. Welfare assessment of cage-free systems should include behavioral observation of dust bathing frequency.