Published in the Journal PLoS ONE 2010
There’s lots of research that confirms the relationship between chronic pain and a change in the behaviour and mood of humans, however until now there wasn’t any proof that the same was true for horses.
A group of French researchers recently completed a study and have demonstrated a clear association between discomfort or pain and aggressive behaviour in horses.
Equine behaviour scientist Carol Fureix, PhD, of the University of Rennes in Rennes, France, observed 59 horses (44 geldings and 15 mares that were 5 to 20 years old) living at three different riding centers in France. The horses completed five different standardized behaviour tests that are commonly used in human-horse relationship studies. After the tests were completed a chiropractor assessed the degree of back pain (or lack of back pain) based on bony and soft tissue palpation and stiffness.
What they found was:
• 73% of the horses were severely affected by vertebral problems (mainly in the sacral area [croup], followed by the thoracic area [withers to mid-back], cervical [neck] and then the lumbar spinal area [mid-back to croup].
• More than 75% of the severely affected horses showed aggressive or negative reactions towards humans in one or more of the five behaviour tests (eg, looking at the experimenter with ears laid back, threats to bite by stretching the neck or approaching the experimenter with ears laid back).
• Severely affected horses showed fewer positive reactions towards humans, than horses that were unaffected or only slightly affected (eg, looking at the experimenter with ears upright, approaching with upright ears, sniffing, licking, nibbling, chewing).
According to the author, this confirms the hypothesis that there is an association between chronic pain or discomfort and aggression in horses.
Fureix noted, “Human awareness of this association may well alter the perception humans have of ‘bad tempered’ animals. Chronic pain should not be overlooked as a cause of aggression in horses”.
The following common behavioural test was used in the above study:
• A motionless person test – person enters the horse’s stall and stands with back against the closed door for 5 minutes, facing into the stall with eyes to the ground
• An approach contact test – person enters the stall and stands motionless 1.5metres from the horse until it resumes eating, the person then comes closer and tries to touch it’s neck. The experiment is stopped when the experimenter can stroke the neck continuously for two seconds
• A sudden approach test – person walks slowly and quietly along barn aisle and appears suddenly at the closed stall door while the horse is feeding
• A saddle test – the sudden approach test is repeated however this time a saddle is carried on the right arm and the stall door is opened
• A halter test – person enters the stall carrying a halter and approaches the horse at a slow walk towards the left shoulder, then puts an arm over the horse’s neck and fits the halter
Comment: We all know that when a horse suddenly starts bucking and pig rooting, for no obvious reason, that we should check their saddle as it may be pinching or rubbing, which can cause pain. When a horse tosses or shakes its head, when we’re riding, we know that the first thing to check is the horse’s mouth…just incase the horse has developed sharp edges on its teeth. So it makes sense that when a horse is showing signs of generalized aggressive behaviour that we should find out if chronic pain is the cause.