Play behaviour in pigs is a reliable positive welfare indicator; its presence signals sufficient resources, good health, and positive affective states, while its absence signals welfare problems.
Play behaviour serves as a valuable welfare indicator because it is sensitive to multiple dimensions of welfare simultaneously. A pig that is in pain, ill, overcrowded, or thermally stressed will not play. Play requires surplus energy and resources beyond basic survival needs, and it is associated with positive emotional states. Its measurement in farm settings provides an integrative welfare signal that captures outcomes from multiple management inputs. The absence of play in commercial pig populations, which is the norm in barren conventional systems, represents a significant departure from the welfare state pigs could achieve. Farms that provide substrate enrichment and adequate space typically observe spontaneous play behaviour that was absent before enrichment provision, providing visible evidence of welfare improvement. Play measurement is increasingly included in positive welfare assessment frameworks.