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What is cribbing?
Cribbing is a stereotypy (seemingly functionless repetitive behavior) characterized by grabbing an upright object with the teeth and pulling against the object with an arched neck and sucking air. Horses often lick a surface that they are about to use for a cribbing bout (Whisher et al., 2011). Horses that crib may spend anywhere from 15% - 65% of their day performing this stereotypy (Wickens and Heleski, 2010). Approximately 4.4% of horses in the US are cribbers (Albright et al., 2009).
Cribbing has not been reported in feral horses that are free ranging (Wickens and Heleski, 2010), therefore it is possible that aspects of management may cause the cribbing behavior. Specific causes of cribbing are yet to be determined and the behavior may be due to a combination of factors. Diet, genetics, boredom, stress, and copying another horse have all been suggested as causes of cribbing (Litva et al., 2010).
Horses that have more grain in their diet have been shown to be at an increased risk of developing stereotypies, while increased roughage in the diet has been associated with a decreased risk of developing stereotypies (Redbo et al., 1998). This holds true for cribbing, as one study found that feeding concentrate to young horses immediately after weaning was associated with a four-fold increase in manifestation of cribbing (Waters et al., 2002). It also seems that the type of grain also plays a role as horses fed sweet feed have been known to crib more than horses fed oats (Whisher et al., 2011).
Whether or not horses learn cribbing behavior from horses that already crib has not been substantiated. In a survey of horse owners, only 1% of horses were reported to have developed a cribbing habit after exposure to another cribbing horse (Albright et al., 2009) making it appear that horses are unlikely to learn cribbing behavior from one another.
Genetics could also play a role, as Thoroughbreds and warmbloods are more likely to crib compared to other breeds (Wickens and Heleski, 2010). A study of horses in Finland found the heritability of cribbing has been estimated at 0.68, which means that cribbing is likely to be passed onto offspring (Hemmann et al., 2014).
Potential ramifications for the cribbing horse
Horses that crib will have increased wear on their incisors. This wear may not cause problems for the horse until they are older and those teeth become in danger of falling out. The additional wear on these teeth may ultimately shorten the life of the horse because they are not able to eat as effectively without these incisors. Additionally, cribbing horses may be harder keepers due to spending time cribbing instead of eating and the increased energy expenditure through the act of cribbing (Wickens and Heleski, 2010).
Cribbing is a risk factor for a variety of conditions. Most notably cribbing horses are at risk for colic (Archer et al., 2008; Malamed et al., 2010). Additionally, it has been found that cribbing horses are more likely to have stomach ulcers than non-cribbing horses (Nicol et al., 2002). Cribbing is even a risk factor for equine motor neuron disease (De la Rua-Domenech et al., 1997). All of these issues contribute to the unpopularity of cribbing horses and a potential reduction in market value (McGreevy and Nicol, 1998c).
Preventing the onset of cribbing behavior
Without knowing the exact cause for cribbing behavior in horses, prevention can be difficult. We do know that cribbing manifests in young horses, typically around 20 weeks of age (Waters et al., 2002) and many of these horses exhibited wood chewing behavior before manifestation of cribbing (Waters et al., 2002). Additionally, reduced risk of cribbing is associated with increased time spent outside, social contact with other horses, and keeping foals solely on grass through the weaning process (Wickens and Heleski, 2010). Once cribbing behavior is established, it is unlikely that a horse will ever completely cease to exhibit the behavior.
Cribbers are different
There are some studies that suggest that cribbing horses may have some physiological and mental differences from their non-cribbing peers.
Horses that crib may also have atypical hormone levels when compared to non-cribbing horses. They have lower plasma levels of leptin, which is a hormone in regulating appetite and the reward center of the brain (Hemmann et al., 2013). These horses were also found to have higher circulating levels of gastrin, a hormone involved in triggering the production of stomach acid (Wickens et al., 2013). These hormone levels may explain differences found between cribbing and non-cribbing horses in learning and stomach ulceration.
Horses that exhibit cribbing behavior may react to situations differently than their non-cribbing counterparts. One study suggests that cribbers learn differently than non-cribbing horses (Parker et al., 2008). However, owners responding to a survey reported that cribbing horses had less anxious temperaments and were equally trainable when compared to non-cribbing horses (Nagy et al., 2010). Another study found that cribbers tend to engage in oral activity when stressed, whereas non-cribbing horses toss their heads or paw when similarly stressed (Nagy et al., 2009). When the cribbing horses were prevented from cribbing, some engaged in other oral activity.
Cribbing may be a way that these horses cope with stress. Cribbing horses actually experience a slowing of heart rate during cribbing (Lebelt et al., 1998). Levels of plasma cortisol, a hormone associated with stress, in cribbers was found to be greater than that in non-cribbers (McGreevy and Nicol, 1998a). Researchers have conflicting opinions as to whether or not preventing a horse from cribbing is stressful for the horse.
These differences should be considered when developing a management plan for these horses.
Managing a horse that cribs
The decision on whether or not to inhibit a horse’s ability to crib should weigh the possibility of increasing stress on the horse against the risk of colic and other health issues associated with cribbing. Many managers also consider the destructive nature of cribbing behavior on barns and fences.
Cribbers are motivated to crib and will work as hard for an opportunity to crib as they will for a chance to eat sweet feed (Houpt, 2012). This motivation makes keeping an established cribber from engaging in cribbing behavior particularly difficult. Many horsemen have tried to prevent horses from cribbing and their creativity can be seen through the sheer variety of methods for preventing a horse from cribbing.
The characteristic cribbing collar is the most commonly used method. These collars generally consist of two straps. One goes in front of the ears and the other behind. The straps hold in place a piece of galvanized steel under the horse’s neck. With the piece of steel in position, it is uncomfortable to flex the neck and perform cribbing behavior. Care must be taken that the collar is properly fitted to reduce tissue damage. Cribbing collars are effective in preventing cribbing in most horses (McGreevy and Nicol, 1998b), but are only effective when the horse is wearing the collar. Horses that are allowed to crib, after being prevented from cribbing for some time, will have an increase in cribbing rate compared to before they were prevented from cribbing (McGreevy and Nicol, 1998b) as if to make up for lost time.
Feeding management is another way that the horse’s manager can affect how often a horse cribs. Cribbing rates increase after a concentrate meal (Gillham et al., 1994), so if possible, formulating diets that contain more forage and less grain can help to mitigate cribbing behavior. Although feeding horses little and often is recommended, cribbing horses fed many small concentrate meals may actually crib more because cribbing is associated with feeding time (McCall et al., 2009). They actually fixate on the feeders and spend more of their time cribbing. The energy and time spent cribbing may make them harder keepers than other horses. Excessive tooth wear may also affect the ability of older cribbers to utilize their diet.
Finally, cribbers should have access to turnout and the opportunity to socialize with other horses. Although, cribbing behavior is not eliminated by providing turnout and companion horses, cribbing rates are reduced (Wickens, 2009). Some cribbers are isolated for fear of the behavior spreading to other horses. It is unlikely for one horse to learn cribbing from another and the cribber’s welfare will benefit from having other horses with which to socialize. If there is a need to keep a cribber stabled, providing a toy has been shown to reduce cribbing rates slightly (Whisher et al., 2011). Turnout, socialization, and prevention of boredom are all forms of stress reduction for these horses.
Other methods of preventing cribbing that are effective, but require intensive management include: elimination of cribbing surfaces, taste deterrents, electrification of cribbing surfaces, pharmaceuticals, oral antacids for foals (Nicol et al., 2002), surgery, and increasing the time spent eating.
Take home message
Cribbing in horses is likely a permanent behavior pattern once established. The exact cause of cribbing in horses remains to be determined, but may be related to management, nutrition, and genetics. Therefore, consider not breeding to a horse that cribs, providing plenty of forage at weaning, and allow horses plenty of turnout and interaction with other horses to reduce the chances of a horse becoming a cribber. Cribbers are more prone to certain health issues, including colic. They may have differences in their learning and how they cope with stressful situations when compared to non-cribbing horses. The decision to inhibit a horse from cribbing should weigh the possibility of increasing stress against the possible health risks of cribbing. Besides inhibiting cribbing behavior, a manager can adjust feeding and turnout conditions to reduce cribbing rates.
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