Cribbing is one of the most common stereotypic behaviors observed in horses. This behavior is not known to occur in feral, free-ranging horses.
Also called “crib biting,” cribbing is when a horse places his upper incisors on a solid horizontal surface and presses down while arching his neck and pulling backwards to contract the muscles. At the same time, the horse makes an audible grunting sound as air is brought into the upper esophagus and then expelled.
Cribbing is more than simply a bad habit because it fits the true definition of a stereotypy, which is “a repetitive, unvarying pattern of behavior with no apparent goal or function.”
Cribbing is identified as an “oral stereotypic behavior.” Repetitive behaviors like weaving or stall walking are known as “locomotor stereotypic behaviors.”
Research conducted to investigate cribbing and other stereotypic behaviors in horses has provided evidence that management practices place horses at greater risk of developing these behaviors, and that these behaviors are also likely the result of underlying physical and/or psychological mechanisms.
Signs Of Cribbing
Each cribber has his own detailed way of performing the action. Some horses will lick and chew extensively before placing their teeth on an object. Other cribbers are very precise about putting their bodies into position, even down to how they place their feet.
Other than the obvious behavior, a cribber often exhibits physical signs, which can include:
- Significant incisor wear (can interfere with grazing, if severe)
- Definitive muscle development (bulging) of the side neck muscles
- Tmj issues (because of the repetitive action)
- History of gastrointestinal problems, such as intermittent colic
- Weight loss (although some cribbers are actually overweight)
- Reduced appetite
Searching For Why
Cribbing has been extensively studied and the behavior may be somehow tied to the brain’s reward system.
“We do have scientific evidence that beta endorphins are involved in the behavior, but the research doesn’t necessarily support that horses are cribbing to get this ‘fix,'” observes Carissa Wickens, PhD, Associate Professor in the Department of Animal Sciences and Extension Equine Specialist at the University of Florida.
“It is more likely that the reward system or reward mechanisms in the brain are altered, so while beta endorphins seem to play a role in facilitating the behavior, the direction of this relationship is still not fully understood,” she notes.
“Cribbers may have something different in their brains that makes them respond to this behavior more than a horse that doesn’t crib,” adds Wickens.
The main theory is that cribbing develops as a coping mechanism for the horse to manage stress or frustration. Some researchers have found that heart rate and levels of the stress hormone cortisol actually decrease when horses are allowed to crib.
Research looked at horses (both cribbers and non-cribbers) in a study where the horses were taught to press a lever in order to receive a food reward. The cribbers continued lever pressing even when there was no food reward.
Wickens notes that there are strong theories with good scientific evidence as to why some horses become cribbers.
“If cribbing is a coping mechanism, the horse developed it for a reason,” she says. Some of the theories that have received attention and scientific investigation include:
- gastrointestinal discomfort may initiate the behavior
- distress or pain early in life alters the horse’s stress physiology
Blaming gastrointestinal issues for cribbing remains a “Which came first, the chicken or the egg?” question.
“Do horses crib because of gastric problems, or are gastric problems a result of cribbing? There are many cribbers who never colic, so there’s not a strong link, although an association between a specific type of colic and cribbing behavior has been identified, “says Wickens.
“It’s not unusual for a cribber to perform another stereotypic behavior like stall walking or weaving,” she adds. “Horses that crib and are fitted with a cribbing collar to limit the behavior will often redirect their cribbing behavior into other aberrant behaviors such as frequent calling/vocalizing or locomotor stereotypies like pacing, stall walking and/or weaving.”
“Some cribbers are just more anxious horses than others, but not all anxious horses become cribbers. We know that environment and management practices can create risk factors for developing cribbing behavior,” says Wickens.
“When we reduce the opportunities for horses to perform their natural behaviors, some horses just aren’t as able to cope, so they develop a coping strategy and for some of these horses, this is cribbing,” she explains.
Researchers believe it is a combination of factors that lead a horse to start cribbing, not just one thing.
There are several risk factors that increase a horse’s risk of becoming a cribber. These include:
- extended confinement
- reduced turnout (reduced grazing and freedom of movement)
- minimized opportunity to socialize
- high-concentrate, low-fiber diet
Cribbing is more often seen in horses that are fed high-concentrate, low-fiber rations from a young age.
“One of the best studies to date was conducted in the UK and followed a large number of young horses from weaning until about two years of age,” says Wickens.
The study, which included 225 Thoroughbred or Thoroughbred-cross weanlings, found that young horses fed high-concentrate, low-forage rations at weaning had four times the risk of developing cribbing behavior.
Can Older Horses Start Cribbing?
Cribbing does appear to be rooted in behavior that starts when a horse is young.
Wickens notes that when researchers talk with horse owners, it seems rare to find a mature horse that suddenly starts cribbing.
“When we do hear stories about older horses that start cribbing, there are increased risk factors,” she says. “These often include a significant change in the horse’s lifestyle. They may have just moved to a new environment where they have reduced turnout or grazing and dietary changes.”
Sometimes the horse has changed hands. Cribbing behavior that was mild in the past — or even unnoticed — can resurface when a horse is suddenly put under different stress.
Some people don’t want their horse turned out with or stabled near a cribber for fear of their own horse picking up the behavior.
There’s very little scientific evidence to support this belief, however.
“Studies show horses aren’t the best at observational learning, which is watching another horse do something and then doing it themselves,” says Wickens. “Most research demonstrates horses have to be exposed to management risk factors to become cribbers.”
She points out that there is also some evidence of a genetic component, which may predispose some horses to developing these behaviors. Wickens notes that most likely, stereotypic behaviors result from a combination of genetic and environmental factors.
Once established, cribbing is rarely completely eradicated.
“The more you can provide turnout, socialization with other horses and either grazing or having forage in front of the horse most of the time, this will reduce the amount of time the horse spends engaging in cribbing, although it may not eliminate it completely,” Wickens notes.
One strategy that is employed to restrict cribbing behavior is to use a cribbing strap/collar.
Cribbing collars work by preventing the horse from expanding his throat at the throatlatch area. In order to do this a collar has to fit correctly and be tight enough.
“Some boarding facilities that allow cribbers will stipulate that such horses have to wear a cribbing collar,” notes Wickens. “If a horse cribs so much that he’s dropping weight, a cribbing collar can be helpful.”
It’s important to understand that because this device is strictly a physical deterrent, the horse will go right back to cribbing when the collar is removed.
Wickens notes that when an owner uses a cribbing collar but doesn’t address any of the other risk factors, this only prevents cribbing while the horse wears the collar.
When horses have to spend extended time in the stall, Wickens suggests providing some form of foraging enrichment activities to promote foraging and more natural oral behavior. This might include slow feeders, lick-it type treats or a forage enrichment ball.
Is Windsucking The Same As Cribbing?
Some of the confusion between cribbing and windsucking is due to people sometimes using these terms interchangeably.
You may have noticed a horse performing a behavior similar to cribbing, but without using his teeth to hold onto an object. He makes the characteristic grunting noise while arching his neck and holding his head in the same position. This behavior is known as windsucking, and like cribbing, it’s not easy to eliminate.
“The windsucker essentially cribs but without having to place their teeth on an object,” says Wickens. “You can see a windsucker doing the behavior even in cross ties, but cribbing behavior appears to be more common than windsucking.”
What About Wood Chewing?
At a glance, someone may mistake wood chewing for cribbing, but the two behaviors are not the same and have different origins.
“Wood chewing doesn’t meet the definition for a stereotypic behavior and is basically a redirected foraging behavior,” says Wickens.
“Wood chewing is a much more natural behavior than people recognize. Donkeys and mules in particular love to browse on brush and bark,” says Wickens. “Horses when turned out will often chew on tree bark, fences and wood structures when they don’t have enough forage.”
If your horse is regularly chewing on — and even eating — wood and/or bark, this is an indication that you should reevaluate your feeding program.
Because studies have shown some horses who chewed wood developed cribbing behavior, wood chewing should be addressed, not ignored.
“Horses are meant to graze and will spend 16 to 18 hours of the day engaging in some kind of foraging behavior when given the opportunity. If you restrict this, they will do something to replace it,” says Wickens, adding that some horses will become more aggressive about wood chewing when they don’t have anything else to do.
Confronted with a wood-chewing horse, many owners will put a hot wire along top fence boards or spray “no chew” products on fences or trees.
“Doing this is like a Band-Aid,” says Wickens. These actions may discourage wood chewing, but don’t address the root of the problem.
“These horses likely need more forage and we also need to look for ways to let horses behave more like a horse. This includes more turnout, socialization and having forage in front of them most of the day,” she advises. “Whenever possible, spreading forage feedings into more frequent meals or using slow feeders to provide longer duration of foraging can help.”
Living With A Cribber
“Of all the stereotypic behaviors, cribbing gets the worst criticism because of the grunting sound and physical damage to facilities,” says Wickens.
She notes that if a cribber is otherwise healthy and doesn’t have incisor wear, letting the horse crib isn’t necessarily a bad thing.
“There are some extremely talented equine athletes and many wonderful recreational horses that are cribbers,” observes Wickens. “It may not be the fault of the current owner who is doing everything right, but when the horse already has this established behavior, then it’s just about managing it.”
Cribbing collars should be considered a piece of tack, meaning they must be kept clean and regularly checked for condition and proper fit. For your horse’s sake, make it as comfortable as possible. This may mean using a fleece insert to avoid sores or wear marks on the skin.