Farm animals have evolved behavioural repertoires that represent fundamental motivations whose frustration causes welfare harm regardless of whether physical needs are met.
The concept of behavioural needs has fundamentally changed animal welfare science. Earlier frameworks focused primarily on physical needs — nutrition, health, freedom from injury — but neglected the psychological costs of denying motivated behaviours. A laying hen in a battery cage may be physically healthy but cannot express the pre-laying behaviour sequence that is strongly motivated and whose denial causes measurable distress. Recognising behavioural needs as welfare-relevant forces a reassessment of intensive systems that meet physical needs while denying core behavioural motivations. The welfare implications are significant: physical health is necessary but not sufficient for good welfare, and many intensive systems that satisfy the former while denying the latter impose genuine welfare costs.