THE question of whether a horse or pony is in pain is one I am frequently asked. As a vet, it is always a challenge to answer this question as accurately as possible. Getting it right can be far from straightforward. Diagnostic tools, such as high quality digital x-rays and endoscopes make it possible to visualise abnormal structures, however, it is much more difficult to interpret how the horse or pony feels about the things we find.
As vets and owners, it is our responsibility to safeguard the welfare of our equine charges, as Roly Owners, CEO of World Horse Welfare puts it: “We (should) do all we can to make the most of horses, while never losing sight of the need to protect their welfare, no matter what the commercial and competitive pressures may be, or what role these horses may play.”
With this in mind, we must endeavour to neither miss the pain signals. Pain is described as an unpleasant sensory and emotional experience associated with actual or potential tissue damage, or described in terms of such damage (International Association for the Study of Pain). Horses in the wild are prey animals and, as such, cannot afford much visible pain behaviour, donkeys are widely regarded to be even more stoic than horses. In practice, this means that equids are very well adapted to masking pain and giving the appearance of health. Horses with severe dental disease will often continue to eat and tolerate being ridden.
The relation between pain, physiological stress and behavioural distress is complex, as there is frequently overlap between the outward appearance of a horse in physical and psychological distress, leading riders to wonder if they are faced with a painful horse or a horse with a behavioural issue. It makes sense to rule out physical pain first before moving on to a behavioural expert. Regrettably, this is not always an easy process. It is extremely difficult to assess pain in an objective, measurable way, particularly at the lower end of the pain index.
So what are the current methods of assessing pain in horses?
– Heart rate and Respiratory rate – These parameters increase when a horse experiences pain, however, they can also be altered by ambient temperature; the horse’s environment; hydration status and disease.
– Stress hormones – These can be altered by the environment and psychological state of the horse.
– Behaviour – Breed, temperament, sex, age and familiarity with environment all impact on a horse’s behaviour and can disguise or mimic pain. Knowing how healthy horses behave is essential to our ability to detect variations from normal. This is often helped by familiarity with each individual horse(s).
– Facial/ Grimace Pain Scale – There has been a considerable amount of research* in this area in the last few years. Pain is diagnosed and graded by evaluating the appearance of the visual structures, whole body behaviour and particularly the facial expressions.
Facial pain markers do not indicate the site of pain. They are general indicators that a horse is experiencing pain and then it is up to veterinary professionals to find the source. Key features of facial markers of pain include, asymmetric/ low ear position (one or both held back); tension around the lips and muzzle; an ‘angled’ eye with eyelids drawn up; squared appearance to the nostrils and a withdrawn or intense stare. Note that not all of these features are present in all cases of pain and I have found that often it is only after the horse has been successfully treated and the horse/ pony becomes pain free that owners realise in hindsight that they have been exhibiting behaviour consistent with pain.
Let’s do our best to interpret the signals that horses send our way.
*Studies by Dalla Costa et al (2016) and Gleerup et al (2015)