Pica is the medical term for the voluntary ingestion of nonfood material. In horses this is usually wood chewing or chewing on the bark, feces (i.e., coprophagia), or tail chewing. Also seen is the consumption of dirt and rarely flesh of other animals. This article discusses the common presentations, what is known about the causes, possible treatments, and prevention for the above conditions.

It has often been conjectured that pica results from a nutrient deficiency that the horse is trying to meet. In a well fed horse this is probably the exception and not the rule and behavioral causes like boredom or nervousness should be considered. Certainly horses on starvation diets will seek any possible source of nutrients. Horses without adequate access to good pasture may not get enough chewing time and exercise which stimulates all forms of pica but particularly wood chewing.

With the exception of salt horses do not develop specific dietary wants, other than a generalized hunger, based on specific deficiency or need. It has been noted that horses with protein deficiency are more likely to engage in coprophagia. In large surveys the following have been noted as risk factors:

• Confinement in snow covered or muddy paddocks
• Restricted intake or lack of roughage, protein, vitamins, mineral, or energy
• Dressage horses (20% wood chew)
• Eventing horses (15% wood chew)
• Late winter or cold, wet weather
• Gl disease or treatment with antibiotics
• Low serum iron and copper levels (consider lack of trace minerals in the diet)