Pigs often mask pain as a survival adaptation, making validated pain assessment tools essential for identifying and treating suffering that would otherwise go unrecognised.
Pig pain assessment welfare challenges arise from the evolutionary psychology of a prey species combined with the economic pressures of intensive production that limit time for individual animal observation. Pigs that are in pain do not generally vocalise or show the obvious distress signals that humans find most compelling. Instead, they show subtle changes in facial expression, posture, movement, and social behaviour that require training to recognise. The Porcine Grimace Scale provides a validated tool that trained observers can use to identify acute pain reliably. The challenge is scaling this training and recognition capacity across an industry with high labour turnover and limited time for individual animal assessment. Automated recognition systems using computer vision trained on grimace scale data offer a promising pathway to continuous pain monitoring at commercial scale.