How to recognise pain in horses from their facial expressions *H&H VIP*

  • Horses are remarkable in the spectrum of facial expressions that they can exhibit. But have you ever wondered why they change their expression? Or asked yourself why your horse always seems “grumpy” when tacked up? Here at the Centre for Equine Studies at Animal Health Trust in Newmarket, we recently developed an ethogram — a description of behaviour (see below) — for the facial expressions of ridden horses. Using this ethogram, we investigated whether we could determine the likely presence or absence of lameness based on analysis of a series of photos for each lame and sound horse.

    Photos were acquired during a work period, so for each horse an average pain score was calculated based on the series of images. There were significant differences between the scores of lame horses versus sound horses.

    A subset of the lame horses was also assessed after the pain causing lameness had been removed using nerve blocks. The facial pain scores were significantly reduced after improvement in the lameness, providing strong evidence that the changes in facial expression were pain-related. Some of the lame horses were also evaluated standing still with a rider; their pain scores were much lower than when working, indicating that exercise — not the mere presence of a rider — was inducing pain.

    We used photos for the study so that the head could be examined independently of the rest of the horse. This ensured that the assessor could not be biased by watching how the horse was moving and his behaviour. The same observations can easily be made in real time, however, observing the whole horse.

    Watch and learn

    Studies have shown that approximately 47% of the sport horse population is lame. Lameness is the reason why around half of the horses undergoing pre-purchase examinations are not recommended for purchase.

    Yet it appears that riders and trainers fail to recognise lameness. Changes in behaviour and facial expression might be easier to perceive, making people aware that something is not right.

    Look at your horse in the arena mirrors as you ride, or ask a friend to watch. Feel if he is opening his mouth or pulling the bit more to one side, or note if he tips his head or gives clues with his ears. It is important to work through his repertoire, because pain may only show in specific conditions.

    Does he put his ears back and open his mouth in canter, but not trot, for example? Or is his head carriage unsteady on the right rein but not the left? Noticing these signs and investigating may help to identify an underlying problem, so that training can then be adjusted to prevent further injury.

    Our study evaluated horses working on the flat, but I believe that most of the results are transferable to jumping.

    Most horses have their ears forwards or erect and their mouth shut approaching a jump and during take-off, in the air and landing. Some normal jumping horses work on the bit on the flat, but adopt a higher head and neck position approaching a fence — so head position alone at this point would not be a reliable indicator.

    The results are not necessarily transferable to situations when horses are performing as a group, however, be it playing polo or racing, because inter-horse reactions may be overriding.

    Horses that buck through excitement usually have their ears forward and other aspects of facial expression indicate that they are pain-free. Yet those that do so due to pain have alterations in facial expression that reflect this. Such behaviour is often a reflection of pain in the sacroiliac joint region and can be abolished with local anaesthetic solution. Many owners have misinterpreted this as a behavioural issue, so it can come as a relief to pinpoint the real source of the problem. This is why recognition of alterations in facial expressions is helpful for early diagnosis.

    Subtle signs

    Horses vary in temperament, but I do not believe that any horse is inherently grumpy. Yet I hear repeatedly from owners, when I acquire a history of a horse to investigate a performance problem, that he has never been willing and that his grumpiness has recently got worse.

    It has been suggested that good horse people can identify subtle signs that something is amiss. In my experience, this is not always true. These signs are ignored as a manifestation of behaviour, rather than a reflection of pain. Trainers have recommended a stronger bit, longer spurs or two whips, which does not resolve the issue, and in pushing the horse through his training has caused more severe injury and a reluctance to work.

    Other horses in pain react with tension and increased speed, also in association with changes in facial expression. Rushing is often seen as an avoidance tactic, but could the horse literally be running away from pain?

    The veterinary profession is also guilty of failure to recognise pain. It is widely assumed that if a horse has musculoskeletal pain, lameness will be apparent when he is in-hand or on the lunge. Yet many lamenesses are only apparent when the horse is ridden and sometimes only under specific circumstances.

    Riders become frustrated when they recognise a change in a horse’s ability to work correctly, but many vets are unable to detect this. Vets must learn to recognise the presence of pain by appreciating behavioural manifestations — and be prepared to refer such horses to specialists.

    The lameness may be subtle, but is often accompanied by changes in facial expression. The horse is trying to communicate with us; we just need to learn what to look for.

    What to look out for

    The ethogram comprises a detailed description of key points:

    • the position of the horse’s head and each ear
    • whether the eye is open or shut
    • the expression and position of the eye
    • whether the mouth is open or shut
    • the position of the tongue
    • the shape of the nostrils and muzzle

    In the study, supported by World Horse Welfare and the Saddle Research Trust, each feature was allocated a pain score from zero to three. Both ears forwards was scored zero, for example, while both ears back was a three. The total score for facial expression at any one time was calculated, based on the analysis of a photo of the horse’s head.

    Features that occurred most frequently as a reflection of pain were: being severely above the bit; tipping or twisting of the head; asymmetrical position of the bit; ear position and eye features — exposure of the sclera (the white of the eye), the eye partially or completely closed, muscle tension behind the eye and an intense stare.

    No single feature was taken in isolation. So if a horse puts his ears back momentarily while the rest of his facial expression is normal, this probably means nothing. If every time during a trot-canter transition he puts both ears back, comes above the bit and opens his mouth, however, this probably reflects pain.

    Ref Horse & Hound; 10 August 2017