Dust bathing prevents feather ectoparasite build-up and plays a key role in maintaining feather condition; its absence in bare systems contributes to poor plumage and welfare.
Dust bathing serves a direct physical welfare function by maintaining feather condition and reducing ectoparasite load. When hens cannot dust bathe, feather quality deteriorates and ectoparasite burden increases, both of which cause discomfort and health effects. The compulsive nature of the behaviour — performed on bare surfaces in the absence of substrate — shows how motivated hens are to perform it. Providing appropriate litter substrate that allows genuine dust bathing meets both the behavioural motivation and the physical maintenance function simultaneously, with measurable welfare benefits.