As horse owners, we often hear that crib-biting is just a “stable vice,” the result of boredom, or simply a sign of gastric ulcers. But if you have treated the ulcers, provided your horse with companionship, and it still crib-bites - you are not alone. Modern science shows that crib-biting is a complex disorder with roots deep in the horse’s biology, genetics, and… brain.
Here are 5 surprising causes of crib-biting that are rarely discussed:
1. A “brain on a high” - the dopamine trap
Crib-biting is not just a neck movement. It is an activity that literally changes the chemistry of the horse’s brain. During crib-biting, there is a release of dopamine, the reward hormone, and beta-endorphins, the body’s natural painkillers. For the horse, crib-biting becomes a form of addiction - the brain creates so-called “super pathways” that make this activity extremely satisfying and calming in moments of stress. That is why physically restricting crib-biting, for example with collars, often creates even greater frustration in the horse.
2. Genetics: Can a horse be “born” a crib-biter?
Many of us worry that a healthy horse will “learn” crib-biting from the horse in the next stall. Research is reassuring: only 1% of horses acquire this behavior through observation. The real culprit is genetics. The heritability of crib-biting is estimated at as much as h² = 0.68. This means that some breeding lines, especially Thoroughbreds and warmbloods, are biologically more prone to developing this stereotypy in response to stress.
3. Childhood trauma (weaning)
The moment a foal stops drinking its mother’s milk is crucial. Naturally, this process lasts around 9–10 months. In breeding practice, however, it often happens as early as 4–6 months of age. Weaning too early and too abruptly, combined with confinement in a stall and feeding concentrate instead of grass, dramatically increases the risk of crib-biting. At this stage, the young horse’s brain is so plastic that this stress may permanently “program” a tendency toward stereotypic behavior.
4. The gut-brain axis and the microbiome
Did you know that the bacteria in a horse’s gut can affect its behavior? Research has shown that crib-biting horses have a different gut flora composition than healthy horses. Diets high in starch, such as oats and pellets, and low in fiber reduce the number of “good” bacteria and lead to the production of metabolites that may irritate the horse’s nervous system. Crib-biting can be an attempt to cope with intestinal acidosis and discomfort that is not obvious at first glance.
5. Hidden deficiencies (magnesium and selenium)
Science points to one more clue: minerals.
- Selenium: Crib-biting horses often have significantly lower selenium levels in their blood serum. Selenium protects neurons against so-called oxidative stress, a deficiency may lead to damage in the brain centers responsible for impulse control.
- Magnesium (Mg²⁺): This is a natural stabilizer of the nervous system. A magnesium deficiency causes synapses in the brain to function “too loudly,” making the horse more excitable and more likely to fall into repetitive habit loops.
What can we do as owners?
Instead of fighting the symptom with collars or surgery, let us focus on the causes:
- More chewing: A horse salivates, producing saliva that buffers acid, only while chewing. Hay ad libitum is essential.
- Less sugar: Starch and molasses “boost” the brain’s reward system, increasing the urge to crib-bite.
- Movement and friends: Free movement in pasture lowers cortisol levels and satisfies the horse’s natural species-specific needs.
- Smart supplementation: Check the selenium and magnesium levels in your horse’s diet in consultation with your veterinarian.
Crib-biting is a signal from the horse that its biology is trying to cope with its environment. Understanding these mechanisms is the first step toward improving the welfare of our horses.
Bibliography and sources:
Wickens, C., & Heleski, C. (2010). Crib-biting in horses: A review.
Albright, J. D., et al. (2009). Crib-biting in US horses: breed predispositions and owner perceptions.
Hemmann, K., et al. (2014). Heritability of crib-biting behaviour in Finnhorse population.
Omidi, A., et al. (2017). Potential link between selenium and cribbing horses.
McBride, S. D., & Hemmings, A. (2005). Altered dopamine receptor patterns in crib-biting horses.
Martínez-Aranzales, J. R., et al. (2024). Fecal microbiome and functional prediction profiles in crib-biting horses.
Waters, A. J., et al. (2002). Factors influencing the development of stereotypic and redirected behaviours in young horses.
Sheldon, S. A., et al. (2019). Effects of magnesium on behavioral responses in horses.
Seabra, J. C., et al. (2021). Systematic review of factors affecting the development of abnormal behaviors in equids