Play behaviour in pigs is a reliable indicator of positive welfare states — its presence signals that animals have the physical and psychological resources to express joy.
Play in pigs is not a luxury or a trivial behaviour — it is a meaningful signal that the animal's needs are met sufficiently to allow positive engagement with its world. A pig that plays is a pig that has surplus energy, adequate social relationships, physical comfort, and an environment complex enough to invite exploration. The absence of play in barren intensive systems is not evidence that pigs in those conditions are content — it is evidence that their circumstances do not permit the expression of positive states. Monitoring play behaviour is one of the most practical and accessible positive welfare assessments available on farm.