Pigs that play are pigs that are thriving. Play behaviour in pigs is a sensitive indicator of positive welfare state and its absence signals environmental deficiency.
Play is not a trivial behaviour — it is a welfare indicator of genuine significance. Animals play when their basic needs are met and they have positive emotional states. Piglets in barren environments do not play; those in enriched, appropriately sized groups with rooting substrate and space play frequently. Measuring play frequency is a non-invasive, welfare-sensitive assessment tool that is increasingly used in certification auditing. The presence of play tells us not just about the absence of suffering but about the presence of positive experience.