Q: Is bamboo, either fresh or dried, hazardous to horses? I have it growing all over my property and baled in with my hay. Is it toxic or could it cause impaction colic? —Name withheld on request
A: The largest members of the grass family, bamboos (Bambusa species) are one of many grass species that can contain cyanogenic glycosides. These compounds, which may cause poisoning in ruminants, are found in some invasive bamboo species. Poisoning is unlikely in horses, however, because the equine digestive system does not break cyanogenic glycosides down into hydrogen cyanide (prussic acid), which is responsible for fatalities. The levels of the cyanogenic glycosides are generally much reduced in the dried plant.
Common bamboo (Bambusa vulgaris) has been reported to cause neurologic signs (incoordination, depression, difficulty in chewing and swallowing) in horses fed large amounts (15 to 30 pounds of the fresh, green bamboo leaves per day for 30 days). The toxin in bamboo responsible for the neurologic signs has not been identified, and is not associated with cyanide. Horses fully recover once they are fed a nutritious diet.
Because bamboo tends to have woody stems, it is possible that a horse eating large quantities may develop an intestinal impaction. Ensuring that the pasture has plenty of good grass will reduce considerably the risk of horses eating enough of the bamboo to cause harm.
Anthony Knight, BVSc., MS, DACVIM
Colorado State University
Fort Collins, Colorado