Stereotypic behaviour is sadly rather common in horses. These behaviours used to be called ‘vices’ until researchers realised that such annoying behaviours are not the fault of the horse, but are caused by inappropriate management and/or feeding. Stereotypic behaviours include crib-biting and windsucking (like cribbing but the horse doesn’t grip onto anything), wood chewing, box walking, weaving, and nodding. Crib-biting and wood chewing are thought to be caused by inappropriate diet and feeding management, whereas box walking, weaving and nodding are thought to be caused by frustration at inhibition of movement.
Estimates of how many horses crib bite vary, but around 4% of the equine population in various countries has been reported to be affected. Much higher numbers did so in studies of young foals carried out over several years. Owners’ perception is that the behaviour lowers the commercial value of the horse and that their exercise performance will be detrimentally affected. In reality, crib-biting horses are at a higher risk of certain types of colic and gastric (stomach) ulceration, and these could reduce performance.
When a horse cribs, it takes hold of something with its front teeth (incisors), arches its neck and draws air into its upper throat with a grunt (the air is not swallowed). The behaviour does get removed from its original trigger as time goes by, so once it is established it can be impossible to stop. The propensity to crib-bite could be inherited, but trigger factors seem to be involved in the onset of the behaviour.
Saliva is produced when a horse crib bites, and some researchers propose this is partly why horses develop the behaviour. Saliva buffers stomach acid and could reduce discomfort in a fasted horse, one fed too little forage and/or one fed large meals of starchy (grain-based) concentrate feed. Crib-biting horses seem to produce less saliva when eating compared to those who don’t crib bite so this may also be involved.
Feeding plenty of forage and limiting starchy grain and grain-based feeds is important to help avoid the development of crib-biting, and to reduce the motivation to crib for horses who crib-bite. Horses fasted for periods of over 4 hours and those fed large starchy (grain-based) meals are at a higher risk of stomach ulcers and developing crib-biting. This is especially true for stabled horses who are kept in isolation. Researchers have shown that straw bedding reduced crib-biting, probably because it was a source of dietary fibre, and that feeding grain-based feeds directly after weaning resulted in a four-fold increase in risk of a young horse starting to crib-bite. Crib-biting often starts very early in a horse’s life, and excess stomach acid in a foal whose dam doesn’t supply enough milk or one who is weaned abruptly could be a causative factor.
Crib-biting horses with high energy requirements should be fed the highest energy forage available, and compounds containing highly digestible fibre and oil, and low starch levels. Vegetable oil can be added to the feed to supply extra energy. Feeding antacids can reduce crib-biting, but they do need to be fed regularly. Anti-cribbing collars should not be used because they cause frustration, probably worsen stomach ulceration and gut discomfort and could be considered inhumane.