Chew on this - The difference between a bad habit and a behavioral disorder
Ken Marcella, D.V.M.
When you're nervous or anxious, do you exhibit behavior rarely apparent at other times? Do you, perhaps, chew on a pen cap, play with keys in your pocket or twirl a few strands of hair?
Most of us do. And many horses also exhibit anxious traits.
It's estimated that 15 percent of domestic horses exhibit similar behavior, called obsessive-compulsive disorder (OCD). This includes cribbing, pawing, weaving, blanket-chewing, head-bobbing or other repetitive actions.
These are often referred to as stable vices, but are actually different. Vices are unwanted and undesirable reactions that can be corrected through proper handling and training. Obsessive-compulsive behaviors are abnormal expression of normal behavior.
Cribbing is an obsessive-compulsive behavior. The cribber uses its upper teeth to grab a stationary object, such as a fence board, then arches its neck, pulls backwards while swallowing air and grunting. (A wood chewer, on the other hand, actually chews and destroys fence and stall boards.) Cribbing is not only rough on barns and fences, but it also may be detrimental to a horse's health. The horse wears down his teeth and swallows air which can lead to inappropriate digestion and colic. Some equine insurance companies won't provide insurance for cribbers.
It's not known what causes OCDs in horses. There may be 30 horses in a barn with the same management, but only two will crib; how each individual handles stress plays an important role.
There appears to be an inherited susceptibility to stress in horses, so genetics are part of the answer. Improper diet and feeding practices are commonly cited as factors that may lead to cribbing.
OCDs have not been reported in free-ranging wild or semi-wild horses. These animals live as horses have lived for thousands of years. They spend 90 percent of their time grazing, and the action of using upper teeth to grab and pull on plant material is routine.
Horses have small stomachs so wild horses are constantly using their mouths and always have full stomachs.
Domestic horses -- especially those kept in stalls all day -- spend less than 30 percent of their time eating and often have empty stomachs. A horse's inability to graze can be a significant stress that is commonly thought to lead to repetitive cribbing behavior.
That cribbing can be greatly reduced by allowing horses more pasture time seems to support this view. Many stall cribbers do not crib in the field, though the worst cases will crib inside and outside.
Reducing stress does not always stop the behavior. In these cases, cribbing horses are sometimes fitted with thick straps that put pressure around the neck and prevents the horse from using the muscles necessary for cribbing.
The straps have several configurations, from severe ones with metal pins that pinch if the horse tries to crib, to a collar that places pressure over the forehead to stop the behavior, which some claim is more humane.
There are surgical procedures in which muscle is removed to stop the behavior. They are disfiguring and do little to address the cause.
New research with drug therapy shows that repetitive behavior may cause the body to release natural painkillers called endorphins. When the horse cribs because of a stressful environment, it releases endorphins, which reduce the stress and make it feel better. Drugs that block the body's release of endorphins can stop cribbing.
Injecting drugs such as Naloxone, or some other anti-depressant, may stop cribbing. Such drugs are short-acting and therefore impractical, however. More research is being done to create similar, longer-acting drugs.
Finally, please stay away from electro-shock collars used to discourage cribbing. I agree with Dr. Nicholas Dodman, professor of veterinary medicine and director of the Animal Behavior Clinic at Tufts University, who categorizes this as a "hideous idea" that does not work.
To reduce cribbing...
• Provide companionship
• Allow time to graze and roam
• Train and handle consistently and intelligently
• Feed less grain concentrate (consider using higher-fat rations)
• Feed more roughages (consider using forage supplements)
Ken Marcella, D.V.M., is based at the Chattahoochee Equine Center in Canton, Ga.