Crib Biting in Horses

Crib biting can be described as the action whereby a horse grasps a solid object with his teeth, arches the neck and draws in an amount of air into the cranial oesophagus, although it is not actually swallowed. This type of behavior is often referred to as a stereotypic behavior – an action which is “repetitive and invariant with no obvious goal or function” and can be indicative of a situation in which the animal lacks a certain degree of control over its environment. Stereotypic animal behaviors have been compared to obsessive-compulsive disorder and disorders involving similar repetitive or compulsive behaviors in humans. As Freud described compulsive behavior, "the patient is impelled to perform actions which not only afford him no pleasure but from which he is powerless to desist."

Over 15% of domesticated horses have been reported to exhibit what are commonly termed ‘stereotypies’. Furthermore, 5% of all domestic horses exhibit crib-biting behaviour. Four behaviours are most commonly described as stereotypic in the horse: weaving, an obvious repetitive lateral swaying movement of the head, neck, forequarters and sometimes hindquarters; box walking, circular route tracing within the stable; crib-biting, grasping and windsucking, a similar behaviour in which no object is grasped before the characteristic grunt is made. Because of their similarity, the latter two behaviours are commonly classed together in many studies. The old adage that an animal develops this type of behaviour due to boredom has been shown to be both too generalized and not entirely scientifically correct. There are, in fact, multiple causes for this type of behaviour and studies are ongoing to try to find a trend in causative factors.

There seems to be a strong link between diet and the development of crib-biting, especially in the young horse. Young horses that are fed a high grain, low roughage diet seem to be more at risk for developing this behaviour. Studies have also been done to try and establish whether young horses with ulcers are more prone to crib-bite, the theory being that the action of crib-biting produces more saliva and thus an attempt to buffer the acidity in the stomach. Although it has not been proven conclusively, there is definitely a link between the stomach condition of foals and crib biting. It is thought that the high grain diet fed to young horses will cause increased acidity in the stomach, causing the ulceration and cribbing behaviour. Interestingly, in a study where antacids were fed to a group of adult crib-biters, there was no significant improvement in behaviour. This may be because the behaviour is so entrenched and the endorphin release addiction is established. Wood chewing has also frequently led to the development of crib-biting according to some scientists, thus again exploring the link between a possible lack of roughage and the development of the behaviour. Interestingly, in studies done where various treatment options were tested, the use of straw bedding had a remarkable influence on the reduced cribbing of those horses tested. The conclusion made was that the bedding was being eaten by the horses, thus increasing their roughage intake and amount of chewing being done. Another theory explores the fact that a young horse, being weaned too early and possibly separated from its mother, still has the natural urge to suckle, and will begin chewing at objects to fulfill that need, leading to the cribbing behaviour.

What we do know is that these types of repetitive behaviours cause a release of endorphins in the body, which have a natural sedative and pleasurable effect. The release of the ‘feel good’ endorphins and resulting increase in serotonin levels (much like the pleasure we derive from chocolate!) becomes addictive and the behaviour is thus reinforced until it becomes addictive. Studies have been done on the use of opiate antagonist drugs (for example naloxone) to prevent the uptake of the ‘feel good hormones’ and thus reduce the effect of the behavior have shown very promising results. In one study, Naloxone significantly reduced crib-biting by 84 per cent, with minimal side effects (some noted were some passage of semifluid fecal material, intermittent penile relaxation, and mild sedation. Treated horses responded normally to external stimuli, retained their appetites, and performed appropriately when ridden. Sedation wore off during the course of prolonged infusions.) More work must be done in this field in order to understand its efficacy and study any potential side effects of the treatment. Horses that weave, another stereotypical behaviour) show no improvement when given the drug. In dogs and cats, these types of drugs are being used with great success, along with improvements in management and other therapies to treat compulsive disorders. Stress seems to be a contributing factor to the condition, and often a stereotypic behaviour is the horse’s only way of responding to a situation in which he feels a lack of control or uncertainty.

Epidemiological research has revealed that the provision of low quantities of forage and minimal opportunities for social contact are also associated with a higher reported prevalence of stereotypic behaviour.

The treatment of this condition is multi-factoral. There have been multiple studies on the effect of various attempts to alleviate the condition. Information is contained below which indicates some of the treatments that have been suggested and their effects (note that this is for behaviours across the board):

“Management changes for the control of equine stereotypic behaviour and their reported success, (data from McBride and Long, 2001)”

Reduced time in stable
49.3% prevalence
75.1% success rate reported

Stable toys
12.3 % prevalence
44.7% success rate reported

Increased exercise
1.4% prevalence
100.0% success rate reported

Regular change of horse’s stable
9.6% prevalence
70.1% success rate reported

Increased social contact
9.6% prevalence
70.1% success rate reported

Exercise before other horses
5.5% prevalence
100.0% success rate reported

Feed before other horses
4.1% prevalence
100.0% success rate reported

Increased hay ration
6.8% prevalence
60.3% success rate reported

More varied view from stable
2.7% prevalence
50.0% success rate reported

Use of stable chain instead of a solid door
1.4% prevalence
100.0% success rate reported

Increased size of stable
5.5% prevalence
100.0% success rate reported

Other treatment options have been suggested as follows:

- Cribbing collars

- Reducing the number of surfaces that the horse has to chew onto (by means of options such as electric fencing, grilles, painting surfaces with foul tasting substances)

- Complementary Therapies:

1. Flower remedies –

Use no more than five remedies in combination and dose with five drops twice daily.
· St John's wort, which will help relieve depression and stress - particularly environmental stress.
· Garlic and echinacea, which strengthen the immune system, often weakened by stress.
· Honeysuckle, which helps the horse let go of the past and relieves 'homesickness'.
· Walnut, to help a horse adjust to new surroundings.
· Agrimony, for anxiety.
· Valerian, for stress.
· Snapdragon, specifically for crib biting.
2. Homoeopathic treatments –

Homoeopathic treatments can be given either as tablets or powders twice daily. The ideal potency to use is 30c.

For crib biting, try:
· Lycopodium, for nervy horses who show digestive troubles and where boredom is the suspected cause.
· Argentum nitricum, where the horse seems agitated.
· Sepia, particularly for mares where irritability is a feature.
· Chamomile, to help calm a restless or irritable horse.

3. Aromatherapy -

Massaging the diluted oil blends around the outer ear, cheek and poll areas can help with a wide range of behavioural problems. These include difficulty in loading, crib biting, windsucking, spooking, fear, anxiety and anger arising from past trauma or abuse. In some cases, results will be seen immediately; in others, a course of treatment has to be carried out over several days.

SEDATIVE: lavender, marjoram, neroli, orange
ANALGESIC (relieves pain): clove, ginger, lavender, peppermint

- Administration of Antacid (especially in young horses)
- Administration of Probiotic

The unfortunate situation is that often the horse will continue the behaviour well into adulthood and wil never truly be ‘cured’. The biggest challenge facing the cribber is the excessive wearing down of teeth in the mouth because of the constant gripping on objects. This leads to poor mastication of food and related digestive problems, often leading to loss of condition or even possibly colic in some individuals that may be predisposed. Often the animal will not or cannot ingest enough food to maintain an acceptable body condition, in which case alternative caloric sources like fats and oils should be introduced to the diet. Regular check-ups by an Equine Dentist are vital in maintaining the crib-biter.

There is no easy answer to this problem and I am sure it will always be around, however armed with knowledge, the horse owner will be able to make educated changes to the horse’s management that will hopefully prevent and possibly alleviate the problem of crib-biting.