Horse Side Vet Guide ®

Equine Health Resource

Underbite, Lower Jaw Protrudes Forward (in Adult)

Code Yellow - Contact Your Vet at Your Convenience for an Appointment

Code Yellow - Contact Your Vet at Your Convenience for an Appointment

  • For an assessment of how this will affect your horse's management and performance.
  • If you think your horses may be in need of routine dental care.

An underbite (undershot jaw, sow mouth, monkey mouth) is a case in which the lower jaw (mandible) protrudes out further than the upper jaw (maxilla), causing the lower teeth to protrude forward. It may result from a congenital defect (common miniature breeds), or from injury or trauma to the lower jaw.

In mild cases, horses can process forage just fine. However, sometimes this condition results in uneven wear on the teeth and the development of overgrowths of the molars (cheek teeth) that can inhibit proper grinding.

If your horse has an underbite, your vet should perform regular dental exams to determine whether dental maintenance is required.


Consider whether the horse seems to eat normally. If the horse is a riding horse, realize that malocclusions of the teeth may lead to dental overgrowths and resistance to bitting. Contact your vet with your findings and concerns.


Your vet assesses all the teeth, especially the cheek teeth (molars) and determines the nature of this problem and whether dentistry is required for treatment or prophylactic management of the problem.

Helpful Terms & Topics in HSVGWritten, Reviewed or Shared by Experts in Equine Health

Author: Doug Thal DVM Dipl. ABVP


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