A Slip of the Tongue
by Dr Shannon Lee
A good blood supply enhances healing of this important organ, which has a far greater role than just as an aid to eating.
It is common knowledge that the horse’s tongue is situated between the dental rows of bones that form the jaw, and sits on the floor of the mouth. Some of the muscles of the tongue are attached to the delicate hyoid bones at the back of the jawbones and continue towards the shoulders (homohyoid) and sternum (sternum hyoid) establishing a connection between the tongue, the sternum and the shoulder.
A healthy tongue will appear as pink and moist and, when a horse is sedated, it is the last part of the mouth to lose sensation. It is, however, a very sensitive organ and should be ‘handled’ with care. Damage can be inflicted easily and the old practice of holding or pulling the tongue out the side of the horse’s mouth, as a form of restraint, should be discouraged.
The tongue itself is a large, muscular organ containing blood vessels, nerves and three distinct muscles: the genioglossus, hyoglossus and styloglossus. These muscles control the movement of the tongue, which forms a key component in both the passage of feed in the mouth and in the airway of the horse. When the tongue is pressed flat across the mouth during exercise, it is one of the key factors in preventing displacement of the soft palate, a condition that affects some horses and can lead to problems with breathing during exercise.
Because of its location and size, not to mention a horse’s often clumsy and curious nature, injury to the tongue is not uncommon. The most frequent injury is that of the tongue being bitten during play or eating; this is usually a minor injury that will often result in a scar. More severe injuries can be caused by abrasion on the canine teeth or during accidents involving head trauma, such as floating accidents etc. Sharp or displaced cheek teeth can also cause serious damage to the tongue.
Many severe tongue injuries can be dealt with and repaired relatively easily by an equine veterinarian, due to the good blood supply and heavy saliva flow in the mouth; even serious injuries can often be repaired with little or no long-term problems. Due to the extensive blood supply within the tongue any injury is likely to bleed heavily, and although the amount of blood loss can seem severe, it is generally unlikely to cause serious health issues for the horse.
This horse’s tongue shows the damage and scaring from the incorrect use of a tongue tie. These straps are used to restrict the movement of the tongue, mainly in race horses, to prevent restriction of the horse’s airways during a race.
Photo courtesy of Dr Oliver Liyou.
Horses can cope with the loss of large portions of their tongue, as can happen when a section must be amputated due to severe injury that has compromised the blood supply. Horses that have experienced severe tongue trauma such as amputation or paralysis can usually manage to maintain weight but will often drop feed and be messy eaters.
A horse with damage to the hypoglossal nerve may display partial or total paralysis of the tongue and those that have had extensive reduction of lower canine teeth may no longer be able to keep their tongue in the mouth, as they have relied on the lower canines to prevent this happening in the past. This unfortunate condition has been successfully managed in several horses through crown restoration of the lower canine teeth.
Due to the large number of hours spent grazing - and their curious nature, horses sometimes ingest objects from their environment and these can lodge in the tongue. When this happens, the tongue will often become swollen; the horse may be reluctant to eat or drink and the owner might notice the horse drooling. Diagnosis of this condition is based on clinical signs and a thorough oral exam requiring sedation, a speculum and a good light source. Diagnostic aids like Xrays or ultrasound may also be required. Because horses with such an injury will be reluctant to eat and drink they risk dehydration, so require rapid attention from the vet, which would include protection against tetanus and bacterial infection.
Common sources of foreign bodies include tyre feeders and hay, as well as the chewing of sticks and biting fence posts. Certain types of grass produce seed heads that can penetrate the soft tissues of the horse’s mouth, so it is important for the horse owner to pay close attention to the quality of feed given, particularly during times of drought when feed quality declines.
Horses that display unusual tongue positioning such as poking their tongue out should always have a thorough examination by a vet, with close attention being paid to the fit of any tack used. It should be remembered that one of the main areas of contact of most bits is the tongue and in response to poorly fitted or inappropriate tack the horse may move its tongue to a more comfortable position. This may be perceived as a problem for riders but devices, such as tongue ties, should not be used or used only with great care.
A tongue tie is a device that restricts movement of the tongue, most commonly used in racing to prevent restriction of the airway during exercise. Incorrect use of these devices can lead to severe injury and scarring of the tongue.
Diseases affecting the tongue are for the most part fairly uncommon, however several diseases cause changes to the tongue. These include botulism and wooden tongue, an infection with an organism called Actinobacillus.
Certain parasites can occupy the tongue, including the larval stages of botflys and cysts containing nematode worms. Tumours of the tongue do occur, but again these are rare.
Taste buds are another aspect of the tongue not covered in this article, but it is interesting to note that research has indicated apple flavouring is not one horses tend to like.
The tongue forms an important part of both the horse’s airway and also its ability to eat and, as such, should be checked regularly as part of the horse owner’s basic equine health management daily routine.
These two were actually grabbing each others tongues in a form of play and no injuries were sustained.
Any change in eating or drinking habits or if any disease or injury of the tongue is suspected, it is highly recommended to immediately consult an equine veterinarian, as the tongue may be small but its impact on the horse’s health could be vital.