Abnormal or purposeless stereotypic behavior, wood chewing can also be provoked by very low fiber diets. In one trial a pine wood post was placed upright in stables and the time to consume it was directly correlated to the fibre content of the diet. The lower the dietary fiber, the faster the pole was eaten. The pine basically substituted for the missing fiber.
However, wood chewing is not generally related to low dietary fiber and may develop spontaneously as a stereotypic behavior, often as a prelude to crib biting / windsucking. In one trial 74% of crib biters had previously exhibited wood chewing. The incidence in several surveys varied between 11% and 30% of horses, with a mean age of development around 30 weeks. Oral stereotypies are believed to be associated with feed and feed management but recently the presence of gastric ulcers has been suggested as a possible predisposing factor. Wood chewing may stimulate saliva production which buffers stomach acid, reducing discomfort. Where the problem persists, and it often does, the levels of fiber in the ration along with possible E.G.U.S. should be considered.