Bruxism, also known as teeth grinding, is a commonly observed problem in horses, and is often a sign of physical or psychological discomfort. Sudden onset of bruxism should be investigated in relation to clinical problems, as this is likely to be due to pain. Longer term bruxism can lead to other problems such as wear of the molars and other oral problems that could lead to pain and/or feeding issues.
Bruxism is the medical term given to describe the rhythmic movement (side to side) of the molars (teeth) causing a grinding, crunching or scraping sound.
Teeth grinding may occur only occasionally – associated with certain situations – or may become almost continuous and be an established part of the horse’s behavioural repertoire.
Bruxism is not a specific sign for a particular problem, it is often a sign of a physical or a psychological issue.
Bruxism is frequently an indicator of a painful condition in both foals and adult horses. In foals, bruxism is often associated with the occurrence of gastric ulcers, which is considered to be related to early or sudden weaning and the feeding of concentrates.
In adult horses, repetitive tooth grinding is often observed in horses experiencing local pain, and often once the painful condition has been dealt with the horse stops the behaviour. As in foals, bruxism has been recorded in horses with gastric ulcers. Bruxism is also observed in horses suffering from certain neurological conditions. It is also associated with many other conditions, from dental pain through to lead poisoning.
Teeth grinding is also seen in horses who are experiencing pain associated with being ridden – in this case the cause may be due to the training methods, the equipment or the rider’s behaviour. Discomfort can be expressed by the horse in various ways, and teeth grinding has been suggested as one sign of ill-fitting equipment such as a pinching saddle, tight-fitting nosebands and bit action (although mouthing the bit should be considered distinct from bruxism). There are many anecdotal reports of teeth grinding occurring in association with different bit types. Horses experiencing pain or discomfort will frequently grind their teeth when a bit is placed in their mouth; in addition this sort of grinding may also be caused through tension or conflict.
Teeth grinding where the horse only performs the behaviour in the stable, when being groomed or saddled, may become compulsive. That is, it takes on a repetitive sequence which is relatively predictable. Whilst the behaviour may have originated as a result of discomfort or anxiety, it is suggested it might become emancipated from the cause, and no longer be performed in association with a specific event. In this case, the behaviour becomes an established part of the horse’s behavioural repertoire and its association with the horse’s current well-being is less clear.
Recent studies have also suggested that teeth grinding can increase as a result of anxiety associated with certain equine training methods. One study found that conventional training methods were associated with higher levels of body tension, high head carriage, increased lip movements and increased teeth grinding.
In natural horsemanship using round pen training, the licking and chewing action observed in horses after they have been moved around the pen by a trainer, is popularly considered to be a sign of a horse being prepared to accept the authority of the trainer. However, equine ethologists argue that the behaviours (which can include bruxism) are a sign of anxiety due to an inability to resolve a current conflict (being forced in circles round the pen) and the easing of pressure by the trainer at this time facilitates resolution through appropriate approach behaviour.
Conflict behaviours, such as teeth grinding, are performed by animals when they are unclear about what they are required to do to relieve pressure, whether that be physical pressure (such as leg and hand signals) or psychological pressure (anxiety due to separation). Increasingly equine behaviour scientists are becoming aware of the need to evaluate such stressors and the impact they have on horses during training and competition.
Sudden onset of teeth grinding must be investigated in relation to clinical problems, since it is likely to be due to pain. Longer term more fixed bruxism, with continuous grinding involving the side to side movement of the jaw, may in time lead to wear of the molars and, as such, oral problems that could cause pain and/or feeding issues.
It may also be a sign of stress or discomfort associated with being ridden and this needs to be investigated to find out what aspect of being ridden is causing discomfort for the horse.
A clinical examination should always be undertaken to identify if there is a physical problem with the horse. This includes oral examination, endoscopy to determine if there are indications of gastric ulceration and other clinical investigations and interventions to determine the source of the pain.
If the horse has developed the behaviour over a longer time period, and where the behaviour is associated with being ridden/trained or handled, a full investigation of the response of rider/handler and horse behaviour can often help to identify the cause of the response. This should be carried out with a behavioural expert who can help to assess learned associations and manage the problem with an appropriate behaviour modification programme.
The Association of Pet Behaviour Counsellors (APBC) – www.apbc.org.uk – for information about referred behavioural services in your area.