AS a prey species, horses have evolved to hide signs that they are in pain. In the wild, weak individuals would become a target for predators, so there is a strong selection pressure towards hiding pain. The tendency to hide pain is a trait retained in most domestic horses, and can make it difficult for their caretakers to identify and treat injuries early. Despite this, the recognition of subtle signs of pain may increase treatment options and reduce the amount of time the horse needs off work for recovery.
While most equestrians are able to recognise head-bobbing lameness, evidence suggests that they are perhaps not as good at recognising low grade lameness. It is estimated that up to 80% of behavioural problems, often ascribed to training or rider problems, may be caused by underlying pain. A United Kingdom (UK) study examined 506 sport horses in full work that were described by their owner as sound – they found 47% of these horses displayed some form of low grade lameness or gait abnormality (Greve and Dyson, 2014).
When assessing lameness, the best place to start is by looking at the horse’s face. Facial expression has become a well-established method of assessing pain in a number of animals and non-verbal humans (Gleerup et al., 2015). Pain is an emotional experience and, even when the individual is trying to hide it, there are a number of facial features that are universal indicators of pain.
In a horse that is in pain, the distance between the base of the ears increases and the ears are turned outward. The ears may move in different directions or be positioned asymmetrically. Next, the muscles around their eyes will tighten, the eyelids will be half closed and blinking will become more frequent. The nostrils will dilate and become squarer rather than the normal elongated shape. The lips and chin will become tense, giving a sharper edge to the muzzle and the jaw muscles will become stressed and visible.
A horse may show no signs of pain while standing, but will still need to be assessed in motion. Horses can show lameness when ridden, in hand or both, so it’s important to assess both in hand and under saddle in all gaits. In 2020, vets and scientists developed a list of 24 behaviours that are likely to be displayed by horses experiencing musculoskeletal pain (Dyson and Pollard, 2020). Horses displaying eight or more of these signs were 10 times more likely to have underlying pain. The list included behaviours such as head tilted or tilting repeatedly, head tossing or twisting from side to side, mouth opening and shutting repeatedly, tail clamped or swishing, stumbling or tripping more than once, spooking or sudden changes in direction and rearing or bucking.
The behaviours that can be observed when the horse is in pain are not necessarily linked to limping or the limbs of the horse. Some may assume that the behaviours being displayed by the horse are because the horse is being grumpy or unwilling. However, research indicates that these behaviours are likely to be signs of musculoskeletal pain. These behaviours can be influenced by factors such as an ill-fitting saddle (for both horse and rider), rider size and/ or rider skill. But if the saddle has been fitted by a qualified saddle fitter recently, the rider is reasonably skilled and is the correct height/ weight for the horse, then the likely source of these behaviours is pain.
By taking a whole horse approach and identifying subtle behaviours that are not traditionally associated with lameness, owners can hopefully identify injuries and get the horse treatment sooner. Where owners are finding a horse’s behaviour challenging, it is important to rule out possible sources of pain before focusing on other strategies to manage the horse’s behaviour. This could save time, money and improve horse welfare.
REFERENCES
Gleerup, K., Forkman, B., Lindegaard, C., Andersen, P.H. 2015. An equine pain face. Veterinary Anaesthesia and Analgesia, 42, 103-114.
Dyson, S., Berger, J., Ellis, A.D., Mullard, J. 2018. Development of an ethogram for a pain scoring system in ridden horses and its application to determine the presence of musculoskeletal pain., Journal of veterinary behavior, 23, 47-57.
Dyson, S. and Pollard, D. 2020. Application of a ridden horse pain ethogram and it’s relationship with gait on a convenience sample of 60 riding horses. Animals, 10, doi:10.3390/ani10061044
Greve, L.; Dyson, S.J. 2014. The interrelationship of lameness, saddle slip and back shape in the general sports horse population. Equine Vet. J., 46, 687–694.
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