DR Sue Dyson recently gave a lecture at the CAFRE Greenmount Campus for the British Horse Soceity. The day focused on diagnosing lameness and Dr Esther Skelly-Smith, a leading veterinary surgeon in Northern Ireland, also spoke at the lecture.

Not only is Dr Dyson a leading veterinary surgeon in the UK but she has also conducted a vast amount of research over her career. One area she has focused on recently is whether musculoskeletal pain can influence facial expressions and behaviour of ridden horses.

Dyson is currently head of clinic orthopaedics at the Animal Health Trust (AHT) Equine Clinic in Newmarket.

FIVE PHASE STUDY

Dyson conducted a five phase study to back up her ideas on pain related facial expressions and behaviour. The study included an assessment of the ability of people to assess facial expression based on still photographs.

She created an ethogram, which is a catalogue of facial expressions of different parts of the head. The first stage of testing consisted a range of professionals, from a variety of backgrounds, applying the ethogram to a selection of photographs of ridden horses.

Assessors could identify different expressions in each horse using the ethogram. They identified expressions based on each area of the head such as the position of the ears, whether the nostrils are flared and whether the mouth was open or not, and if so how open it was.

It was a very comprehensive study and showed there was no variance based on professional background. Assessors had the least agreement on the eyes and the muzzle but otherwise analysts found that owners could most likely recognise different expression in their horse’s face using the ethogram.

The study went on to test whether the ethogram could be used to distinguish between lame and sound horses. To do this a pain score of 0-3 was applied to each facial expression (ears, mouth, muzzle etc.), these were then added together to give a total pain score or each horse.

The horses who were being categorised as to whether they were lame or sound were by Dyson ahead of the assessment. The results showed that there was a scientifically significant difference between the pain scores given by the assessors to the lame and sound horses.

The study continued to assessing the horses again after the lame horses had been nerve blocked, which is most of the cases helped to relieve the lameness. The assessors gave once again gave the horses a pain score based on their facial expressions. The pain scores for the horses who were nerve blocked significantly dropped.

Control horses were used in the study. They included horses from a CCI4* event (doing the dressage on grass) and from a CDI Grand Prix dressage competition (competing on an artificial surface). Dyson chose these horses to be part of her control because she knew that they had passed an in-hand trot one or two days previous.

EXAMINING FEATURES

Throughout the study Dyson found that some facial expressions occurred more frequently in lame horses including the mouth being open, tension around the eye and the bit being pulled through more on side of the mouth than the other.

Dyson concluded that when a combination of facial expressions were shown that it was an indicator of pain and the more features you see the more likely that the horse is experiencing pain. She was surprised to find out how many horses had their eyes closed during riding which she deemed to be an indicator of pain.

When questioned on whether the photos of horses with their eyes closed was just down to the timing of the photo Dyson responded by saying that she has never acquired a photo of a sound horse with their eyes closed.