Investigator(s): E. Love, Dr J. Murrell, Dr HR. Whay
The assessment and alleviation of pain in animals is an important part of the veterinary surgeon’s role yet remains a challenge amongst many species. In horses, pain assessment and management has received relatively little attention. Development of such a tool would represent a major advance in pain management in horses and would provide significant welfare benefits.
The use of facial expression to detect and quantify pain in animals is a novel area of research; so far studies have been undertaken in laboratory animals only. The overall aim of this study was to determine if horses have a “pain face”. The horses studied would have their facial expressions measured for any change during a brief painful stimulus, or before and after castration. Findings might then be used to help owners, technicians and veterinary surgeons identify horses that may be in pain, prompting further investigation and resulting in appropriate pain treatment or management.
This study found that horses’ facial expressions change when they experience pain during procedures such as intravenous injections and following castration. For example, an increase in the distance between the medial and lateral aspects of the nostrils, along with either an increase or decrease in eyelid aperture, was measured during insertion of a needle into the jugular vein. For ethical reasons it was important to administer effective analgesics which meant the effect of moderate to severe pain on facial expression was not studied.
It is possible that some of the changes in facial expression were not specific to pain and may have been due to anxiety. However, the ability to recognise a negative state in horses, be it pain, distress or fear, using facial expressions has important implications for welfare.