Grimace scales derived from facial action coding systems have revolutionized pain assessment in animals, enabling more accurate identification of suffering in species ranging from mice to horses, improving veterinary and farm welfare outcomes.
Before grimace scales, pain assessment in animals relied heavily on behavioral changes that require movement - a problem because severely painful animals may become immobile and appear 'calm'. Facial action coding provides a reliable, rapid assessment that can be used by non-specialist farm workers or in clinical settings. Validated grimace scales have led directly to improved pain management protocols in veterinary practice and laboratory animal research. Wider deployment on farms - particularly for post-operative pain management following routine procedures like castration and dehorning - could prevent significant animal suffering.