Vibrissae, also called 'tactile hair' or 'sinus hair', have a different anatomy than the hairs of the tail, manes or coat. Vibrissae are longer and thicker than regular coat hair, hey have a tapered shape and their root lies deeper into the skin. The vibrissae’s hair follicle is about 5-6 times larger than a regular hair follicle. The vibrissae are usually located in groups at specific areas of the body. On the horse, these areas are limited to the head: around the lips, the nostrils and the eyes.
The most prominent anatomical difference between a vibrissae’s follicle and other hair follicles is that a blood filled sinus surrounds the whisker's hair follicle. Nowhere else in the skin do so many nerve fibers come together.
In theory, vibrissae are sensory organs located in places where fast reflexes are important like around the eye, or where sight is limited as is directly underneath and in front of the horse's nose. Horses have an elongated head and their eyes are placed laterally and quite far back. This most probably gives them an evolutionary advantage because it prevents the long grass from obstructing the horse's view when grazing. However, the disadvantage of this design is that the nose blocks their view of what's directly in front or underneath it. Depending on the breed, the anatomical placement of the eyes and how high the horse carries its head, this blind spot can extend up to almost two meters in front of the horse . It is because of this that the horse needs a different way of knowing what's directly in front of its nose. Most likely, the vibrissae around the nose and mouth fulfill this need by creating a zone where the horse, in a sense, has an alternative way of seeing. This way, for example, the horse can be aware of in incoming object.
The sense of touch is variable over different areas of the horse's body. The withers, mouth, flanck and elbow regins are very sensitive areas. Some horses dislike their ears, eyes, groin and bulbs of the heels being touched. As herd animals it is important that they are sensitive to the presence of others at their sides. This may help them to move as a cochesive social group in times of danger and to initiate bouts of mutual grooming.
The vibrissae around the eyes and muzzle have a rich afferent nerve supply. Then aparently disorganized beard of vibrissae in the neonatal foal is thought to facialitate location of the teat.
Vibrissae inform the horse of its distance from a given surface and may even be able to dectect vibrational energy (sound). Together wiht the lips, they gather tactile information during grazing and headrubbing. Horses are said to test lectric fence wiht thes whiskers before touching them. It has been suggested thant the inability to detect fixed object is contributory factor to facial traume in horses subjected to road transport subsequent to wisher triming.
Becasue vibrissae can be identified as anatomically different form normal hair coat, the trimming of whiskers has been outlawed in Germany, France and Switzerland.
Some experts about the whiskers:
"The first thing a wild horse does when it dares to approach you is examine the contours of your face minutely and exhaustively with its whiskers, to know you. Like its eyes, ears and nose, a horse’s whiskers are sense organs, collectors of information. They warn that the sensitive lips are near a surface and assess its form, texture and pliability, allowing the horse to learn what is beneath his nose safely and delicately. We can’t even imagine what else they do: feel air movement or ants in the feed, find where to nuzzle or play a significant role in naso-nasal contact, for instance. But we can imagine that being deprived of a sense organ amounts to mutilation".
Lucy Rees - Ethologist & Horse Trainer.
"If we genuinely care about horses, we need to go beyond our anthropocentric view of what animals should look like. Horse whiskers are there for a reason and should be left there, if we want to help horses to make as much sense as they can of the world around them." Prof Daniel S. Mills BVSc PhD CBiol FSB FHEA CCAB Dip ECAWBM(BM) MRCVS
European & RCVS Recognised Specialist in Veterinary Behavioural Medicine.
"No hamster owner would deprive their hamster of its whiskers for cosmetic reasons. Yet many horse owners routinely do this, only because they think it looks tidy. Perhaps they don't know that horses need their whiskers every bit as much as cats, dogs and mice need theirs. Perhaps they know and they don't care. Domestication has robbed the horse of so much of its freedom to display its natural behaviours. Whisker trimming is one aspect of this problem which could easily be resolved by sending a strong message to horse owners." Julie Kaiser-Hansen - Equine Journalist.
"Have you ever watched a horse pick his favourite bits out of a feed or be able to find small grains on the floor? Their whiskers have a role in detecting different textures, as well as in understanding the space around them. To remove them for competition means depriving your horse of something he very much relies on.” Suzanne Rogers - Animal Welfare Consultant.
"As prey animals horses rely on all their senses to help them decide what is safe and what isn't in order to survive and avoid injury. Removing whiskers prevents a horse's ability to completely evaluate something that may compromise their safety and therefore may contribute to the horse responding inappropriately to a stimuli they may have otherwise have felt comfortable to be around.” Anita Menzies-Udale - Co Founder of The Scottish Animal Behaviour and Rescue Centre.
There are some scientific works about whiskers' mammals:
Specific areas were found on histological sections of the brains of rats, which specialize in the processing of information from the vibrissae .These areas are relatively large because each affected vibrissae is represented by its own separate location in the brain. The fact that such a relatively large part of the cerebral cortex is dedicated to each whisker, gives us an indication of the importance of vibrissae for the rat. In other animals with vibrissae, including horses, it cannot be excluded that they also possess specific areas like these in their sensory cerebral cortex.
Previous research showed that blind rats cross longer elevated gaps when their vibrissae are intact than when they are clipped. Also when confronted with a cliff, rats will only show avoidance behavior when their vibrissae are trimmed.
Then the question is....Why do we trim the whiskers?
References -Vibrissae of the horse, a pilot study on how to assess the effect of manipulation. Utrecht University.
-Equine Behavior. A Guide for Veterianarians and Equine Sicentists. Paul McGreevy.
-Epona.tv