Damage by the bit to the equine interdental space and second lower premolar

Summary Equus caballus mandibles were surveyed in 4 museum collections and 66 domestic horse mandibles were compared with 12 feral and Przewalski mandibles. Periostitis (bone spur formation) of the interdental space (bars of the mouth) was found in not less than 62% of the domestic hemimandibles. Erosion of enamel and dentine was found in 61% of the second lower premolars (Triadan 306 or 406). Eighty‐eight percent of the domestic mandibles showed one or both lesions. The more severe the interdental periostitis, the more likely it was that the 06s were eroded. Twelve feral and Przewalski mandibles were free of both lesions. A clinical examination protocol is described for the identification of bit damage in the live horse. By recommending removal of the bit when damage is found, practitioners can test the author's prediction that the bit is a cause of certain idiopathic diseases and many behavioural problems.