The freedom to express natural behaviours is a core welfare principle for laying hens. Understanding what these behaviours are helps evaluate production system welfare quality.
Natural behaviour expression is not merely an added welfare benefit but a fundamental requirement for animals whose behavioural systems evolved over millennia of selection for specific ecological niches. A hen denied the opportunity to dustbathe does not simply lack a luxury — she experiences persistent frustration of a behaviour system that in the wild would occupy significant daily time and provide both physical and psychological function. The five domains model of welfare explicitly includes "behavioural interactions with environment, other animals, and humans" as a welfare domain equal to physical health domains. Production systems that prevent hens from expressing their full behavioural repertoire are providing deficient welfare regardless of how good their health indicators may be. This framework helps explain why cage-free and free-range systems, when well-managed, provide genuinely better welfare even when disease rates may be higher.