It is natural for horses to browse, chew on tree bark and branches. However, in domestic stalled horses, wood chewing is considered an undesirable (stereotypical) behavior.

Wood chewing is a completely different behavior than cribbing. Wood chewing is actually the consumption of wood, whereas cribbing is strictly a behavior where a horse bites down on a solid object without ingesting any material.

Wood chewing may be dietary in origin, as horses eating low fiber (roughage) diets tend to chew wood more often. Horses on very green lush pasture may chew bark more than on other pasture types. This may be due to reduced roughage content in that pasture. Wood chewing may also be a result of management. Like cribbing, wood chewing is more common in horses that are provided with limited exercise and turnout, high grain diets and limited roughage.

Horses generally tolerate some consumption of some wood without it causing them health problems. However, some trees, wood types, and wood stains and paints can be toxic to horses. Excessive intake of chewed wood can result in intestinal impaction and abdominal pain (colic).