How to identify and quantify pain due to dental disorders in horses?

Dental disorders can cause discomfort and chronic pain, affecting the athletic performance and welfare of the horses. However, dental disorders may not be manifested with recognizable clinical signs and may, therefore, lead to late diagnosis or care. Accurate recognition and adequate quantification of pain in horses is essential for the correct diagnosis and management of different painful conditions. Diverse models of systematic identification of pain have been described for many conditions in horses using vital parameters (heart rate, respiratory rate), behavioral evaluation, endocrine measurements, and facial expression. Pain scales based on facial expression changes have been developed for humans and other species, gaining prominence in equine medicine since it proved to be a sensitive tool that is easy to apply with a little investment of time and training, and high reliability within and between observers.

The present study aimed to evaluate the effect of dental disorders on equine welfare by analyzing the equine facial expression using the Horse Grimace Scale (HGS). Six different facial characteristics were evaluated in 33 adult horses, both males and females, that were regularly involved in sports or working activities. While two of the subjective evaluators identified an improvement, the other two did not. In conclusion, dental disorders result in discomfort or pain and modify the facial expression of the horses. The HGS is reliable for the identification and quantification of pain associated with dental disorders either by face-to-face evaluation or by evaluation of photographs. However, these images are not suitable for subjective evaluation.

Pesquisa realizada no Programa de Pós-Graduação em Ciência Animal (PPGCA/PUCPR), de coautoria de dois coeditores da Revista Acadêmica Ciência Animal, Prof. Pedro Michelotto e Tâmara Duarte Borges, foi recentemente publicado na revista Applied Animal Behaviour Science e está disponível em: https://doi.org/10.1016/j.applanim.2020.104970