Monitoring acute pain in neonatal foals with the Equine Utrecht University Scale for Facial Assessment of Pain for foals (EQUUS-FAP for foals) and the Horse Pain Face for foals (HPF for foals)

Abstract

Animal pain and pain assessment have received increasing attention during the past years. But, objectively assessing pain in horses is difficult, because horses will avoid predation by not openly expressing their pain. Various different pain assessment systems have been described in horses, such as unidimensional pain scales, composite pain scales and facial expression-based pain scales. Although pain assessment in adult horses has been investigated, there is no literature describing pain assessment in neonatal foals. In this study, two facial-expression based pain scales, the Equine Utrecht University Scale for Facial Assessment of Pain for foals (EQUUS-FAP for foals) and the Horse Pain Face for foals (HPF for foals), are constructed and described in neonatal foals. For this study design, 26 neonatal foals aged between 0 and 14 days were used (n=9 patients; n=17 controls). All the foals were filmed in the stable with the mare by an observer outside the box. The video clips were randomized, blinded and scored by means of the EQUUS-FAP for foals and the HPF for foals by three independent observers. Both the EQUUS-FAP for foals and the HPF for foals scores demonstrated high inter-observer reliability (Cronbach’s alpha = 0,97 for EQUUS-FAP for foals; Cronbach’s alpha = 0,93 for HPF for foals) with limits of agreement of 0,97-0,99 for EQUUS-FAP for foals and 0,84-0,96 for HPF for foals (p<0,001). Both HPF for foals and EQUUS-FAP for foals scores showed a high intra-observer reliability (Cronbach’s alpha = 0,98 for EQUUS-FAP for foals; Cronbach’s alpha = 0,94 for HPF for foals) and limits of agreement of 0,97-0,99 for EQUUS-FAP for foals and 0,91-0,97 for HPF for foals (p<0,001). Patients showed significantly higher pain scores compared to control foals (p<0,01 for EQUUS-FAP for foals and p<0,01 for HPF for foals). Nonsteroidal anti-inflammatory drug (NSAID) treatment decreased both pain scores, but differences were not significant (p=0,14 for EQUUS-FAP for foals and p=0,14 for HPF for foals). The EQUUS-FAP for foals and the HPF for foals proved to be useful for pain assessment in neonatal foals in accordance to the inter- and intra-observer reliability and differences between patient and control group. There were differences between scores before and after NSAID treatment, but they were not significant, possibly due to a small number of included animals (n=4). This study demonstrated that both pain scales are reliable for facial-expression based pain scoring of neonatal foals, of which the EQUUS-FAP for foals appeared to be more reliable, repeatable and clinically applicable. Further research in neonatal foals is necessary to investigate validity and practical applicability of both pain scales.