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Also Known As

Overshot jaw, Parrot mouth, Undershot jaw


Although most young horses' mouths and teeth develop in a normal pattern, some horses are prone to an incorrect bite which occurs when the upper and lower incisors do not meet edge to edge as needed for effective chewing of hay and other feeds. This results in a malocclusion.

 Both undershot jaw and overshot jaw are conditions of malocclusion. A malocclusion often results in poor digestion, and, in some cases, malnutrition because the horse has trouble eating or grazing and cannot chew feed well enough for good digestion.

Both undershot and overshot jaw are usually inherited. Many horses have slight malocclusions and the problem is serious only when the misalignment is so pronounced that the horse cannot graze and chew effectively, resulting in uneven wearing of the teeth and other dental problems.

When the conditions are evident in a young horse, they usually become worse as the horse grows and matures.


  • Misalignment of top and bottom jaws
  • Teeth do not meet edge to edge
  • Inability to masticate feed properly
  • Need for frequent dental care because teeth do not wear evenly
  • Teeth grow too long and form sharp hooks that can damage cheeks and/or gums
  • Reluctant to eat
  • Malnutrition


Both undershot jaw and overshot jaw are hereditary and are the result of misaligned jaws and incisor teeth.


Careful selection of breeding stock is the best prevention of these conditions.


Treatment of both undershot jaw and overshot jaw works best if detected by the time the horse is six months old. Wire tension bands from the upper incisors to the first maxillary cheek teeth to slow the growth of the upper jaw sometimes works well to correct overshot jaw.

A veterinarian can devise a treatment based on the conformation of the horse's jaws. If braces are required, they may need to be left in place for several months. Careful monitoring is necessary to make sure no adverse effects occur.

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EquiMed staff writers team up to provide articles that require periodic updates based on evolving methods of equine healthcare. Compendia articles, core healthcare topics and more are written and updated as a group effort. Our review process includes an important veterinarian review, helping to assure the content is consistent with the latest understanding from a medical professional.