Cribbing, also known as crib-biting, is the most common oral stereotypic behaviour seen in horses. Cribbing involves the horse repeatedly and compulsively grasping an object between its teeth and sucking in air.
Horses may crib bite for many hours per day, reducing time for other important activities such as eating and socializing. Cribbing can also contribute to poor body condition, dental problems, and increased risk of gastric ulcers or colic.
This behaviour often begins as a coping mechanism. Addressing possible stressors such as lack of access to forage, confinement, boredom, and social isolation can help to prevent cribbing.
Half of all cribbing cases are believed to start in the first 5 months of life when foals are typically weaned. Allowing a gradual weaning process may reduce the risk.
Your horse’s feeding program can influence the expression of stereotypical behaviours. If your horse is cribbing, submit their diet online for a free evaluation by our equine nutritionists.
What is Cribbing?
Cribbing is an example of an oral stereotypy. It involves the horse grasping onto a fixed object with its teeth, biting down, and gulping air into the cranial esophagus through the contraction of the neck muscles.
Cribbing is closely related to windsucking behaviour, but horses that wind-suck perform this stereotype without grasping objects between their teeth. Many horses display both behaviours.
Cribbing causes a characteristic grunting noise as air is sucked into the esophagus. Contrary to what some believe, the air is not swallowed which makes cribbing distinct from aerophagia.
Horses can crib on any solid object at around chest level, such as a fence board, stall door, or bucket. Cribbing does not involve chewing the object but can cause damage to the environment as the incisor teeth clamp down. Tooth erosion can also occur.
Horses that display cribbing behaviour are highly motivated to perform the stereotype. They can crib-bite for up to 5 hours per day, with some reportedly spending up to 65% of their time on this activity. It is considered a post-prandial stereotypy because it occurs most frequently after a meal. 
Cribbing is not seen in wild horses but has been observed in domesticated horses dating back to 1578.  This suggests that the behavior is related to modern management and feeding practices, although a genetic component may also play a role. 
A stereotypical behavior is a repetitive behavioral sequence with no obvious goal or function. The behaviors are believed to be automated coping responses or expressions of frustration.
Other examples of stereotypic behaviors include:
- Wind sucking
- Wood chewing
Up to 32% of the horse population is thought to display stereotypical behaviour. Crib-biting affects 8.3% of horses. 
Wind sucking is a related behaviour that may occur if there are no surfaces available for a horse to grasp with its teeth or if the biting behaviour is punished.
Wind sucking involves the same contraction of neck muscles and the sucking of air without clamping down on an object with the teeth.
Why Does my Horse Crib Bite?
Stereotypical behaviours may be an indicator of poor welfare, either in the past or present. They are coping mechanisms designed to reduce stress and provide control over an environment.
- Being unable to perform a behavioral pattern the horse is motivated to perform. For example, horses on a forage-restricted diet are not able to perform species-appropriate feeding behaviours.
- Being unable to avoid a fearful or stressful situation. For example, some stereotypies develop in response to negatively reinforced training.
- Being kept in social isolation or long periods of confinement. For example, stereotypies are more common in individually stalled horses.
Physiology of Crib-Biting
Crib-biting and other stereotypical behaviours cause dopamine to be released in the brain. The temporary spike in dopamine helps horses cope with stress.
Dopamine is a neurotransmitter thought of as the “pleasure” chemical. It plays a major role in the reward centre of the brain. 
Chronic stress triggers the release of beta-endorphins, stimulating secretions of dopamine in an area of the brain known as the striatum.
This activates dopamine receptors in the basal ganglia, which is the part of the brain where stereotypies are thought to develop. 
In crib-biting horses, there are more D1 and D2 dopamine receptors within an area of the brain known as the nucleus accumbens. There are also fewer D1 and D2 receptors in the caudate nucleus, a key area for action-outcome learning.
This suggests that cribbing horses are prone to habit formation and are highly motivated to carry out repetitive actions. Horses affected by stereotypical behaviours may also have a reduced capacity to learn and train. 
Chronic stress is thought to contribute to stereotypical behaviours, including cribbing. Other risk factors have been identified including: 
- Breed; Thoroughbreds and warmbloods are up to 3 times more at risk
- Stable management; stabled horses are more at risk
- Weaning experience
- Type of work
- Time of initial training
- Sex; male horses, particularly stallions, are more at risk than mares
Domestic weaning in horses typically occurs at around 4-6 months. In contrast, weaning occurs at 8-9 months in feral horses or domesticated horses allowed to wean naturally. 
Researchers suggest that oral stereotypies, including crib-biting, may develop due to premature cessation of nursing behaviour. General weaning stress and abrupt dietary changes may also play a role. 
Ensuring your foal has adequate access to grass or forage may reduce the risk of cribbing during this dietary transition. You can also ease stress and digestive issues associated with weaning by offering new feeds while the foal is still suckling.
In addition, gradual group weaning significantly reduces weaning-associated stress and related behaviours such as vocalization, locomotion, cribbing. 
The good news is that most stereotypical behaviours can be curtailed within the first 12 weeks of their development, as long as appropriate management practices are applied to remove the causal stressor. 
Horses are herd animals with a strong desire for social interaction. Stabling or turnout with another horse significantly reduces stereotypic behaviors such as cribbing.
One study found that 22% of young horses stabled individually developed crib-biting, whereas no horse in the pair housed group did. 
Isolated housing at a young age is also associated with other abnormal behaviours, including weaving and boxwalking, which did not occur in pair housed horses. In total, 67% of horses that were individually stabled showed stereotypical behaviours. 
Socialization is important for horses, but the wrong social grouping can also cause problems. Horses that are low in the social hierarchy are more likely to experience stress and to have less access to resources including shared feed and water.
Boredom is commonly cited as a reason that horses crib. Horses kept in stalls with limited access to turnout may lack sufficient engagement to support optimal psychological well-being.
If your horse currently spends long periods of time idle, they may benefit from enrichment activities or toys to make their environment more stimulating.
In one study, providing horses with an oral stall toy slightly decreased cribbing rates.