To find out how sensitive horse faces are to pressure, heat, and touch, researchers checked horses’ facial nerve functions. The results could aid veterinarians in diagnosing equine idiopathic headshaking.
Anyone who deals with horses knows that their faces are sensitive. When grooming, a softer brush is used for the head area, and if flies land on their nostrils, they shake them right off. Researchers have now used handheld devices to check the functions of horses’ facial nerves. This involved measuring facial sensitivity to touch, pressure, and heat.
Testing touch, pressure, and heat thresholds
Together with her team, Kata O. Veres-Nyéki, DrMedVet, Dipl. ECVAA, PhD, MRCVS, of The Royal Veterinary College, in Hatfield, U.K., tested facial sensitivity in a total of 34 Warmblood mares, geldings, and stallions between 1 and 23 years old. To test tactile thresholds, they used a thin, flexible stick (von Frey filaments). To test heat thresholds, they pressed a medical heating device (thermode) to the facial skin, which heated from 30 degrees up to 55 degrees Celsius. For the pressure thresholds test, a handheld algometer with a silicon tip was held against the horse’s face. As soon as the horse reacted in any way to any of the test devices, the test was stopped.
Horses become less sensitive with age
Unlike humans, horses are less sensitive to facial contact. One explanation for this is that they cannot say when they feel a stimulus, but can only respond physically. Because of this, it is possible that they may sense a stimulus earlier but tolerate it for a certain period of time.
Gender did not matter in terms of sensitivity threshold. Age, on the other hand, did make a difference. The older horses reacted later to the stimuli than the young horses. The reasons for this are still unknown, but it is suspected that the nervous system becomes damaged with age.
Test results to help veterinarians
Veres-Nyéki welcomes the research. If veterinarians know facial sensitivity values, they can more easily diagnose alterations in sensitivity. It also makes it possible to track the effectiveness of pain-relieving treatments in a non-threatening way.
The most reliable results were provided by tactile sensitivity on the nostril, pressure sensitivity at the temporomandibular joint, and heat sensitivity at the forehead just above the eye. These results may be particularly helpful in the diagnosis of idiopathic headshaking and make it possible to identify facial nerve sensory abnormalities.
Horses should not be body clipped
While there was little difference in testing between horses that were shaved and those that were not, unshaved horses were still more sensitive to touch. Therefore, it is best not to shave horses so as not to lower their sensitivity.
In addition, based on the test results, Veres-Nyéki recommends using gentler equipment, especially on young horses, since they have a lower sensitivity threshold. In general, equipment should not cause pain whatsoever.