The development of the Sheep Pain Facial Action Unit (SPFAU) system has transformed the ability to objectively assess pain in sheep, enabling better treatment decisions and welfare monitoring.
The Sheep Pain Facial Action Unit represents a significant advance in practical welfare assessment. Before objective pain scales, pain recognition in prey species relied on behavioral signs that required experience to interpret. The SPFAU provides a standardised, teachable method that farm staff without specialist training can use to identify animals requiring treatment. Farms implementing the scale have demonstrated earlier intervention and better treatment outcomes. The broader grimace scale programme across species is one of the most important applied welfare science contributions of recent decades, translating pain neuroscience into farm-practical tools.