What is cribbing?
Cribbing is characterized by a horse grasping the edge of an object (stall, feed trough, fence, etc) between his teeth. The horse then flexes his neck and throat muscles while moving his tongue and throat as if he is swallowing. All while doing this he begins sucking in while keeping his neck and throat in a fixed position.
A gush of air will fill the horses upper esophagus which leads to cribbings characteristic grunting sound. Most horses crib in a rhythmic tempo and appear to be completely engrossed in what they are doing.
Ok, But why does my horse do it?
Cribbing does not appear to be caused by boredom or stress. Therefore more roughage, more exercise, and limited stall time does not lead to a decrease in cribbing behavior.
In fact, studies have linked cribbing with soothing the horse. As evidenced by a slowed heart rate, and an increase in blood stream endorphin levels.
One study actually found that blocking the pleasure inducing effects of this endorphin increase saw a DECREASE in cribbing behavior.
This points to the possibility that cribbing is an addiction much like when a human experiences a drug addiction.
Cribbing horses may be motivated by a desire to get "high".
This would mean the horse is cribbing in order to get "high". Therefore cribbing is a form of self stimulation, explaining the lengths a horse will go to crib-bite.
Cribbing Myth Busted
I still hear horsemen and women who believe cribbers swallow air, leading to abdominal issues. The belief is that a cribbing horse swallows so much air that they suffer from poor digestion, flatulence, and colic.
Studies over a decade ago have proven that almost no air is actually swallowed by the horse when cribbing and that these medical issues should not be pegged on the cribbing behavior.
What does all this mean?
Cribbing does not appear to have a direct negative effect on your horses health. However, it can lead to premature wearing of your horses teeth, and to hypertrophy of the sternocephalicus muscle (large muscle on the underside of the horses neck).
It is commonly characterized as a vice do to it's undesirability and the destruction to fences, stalls, and other surfaces.