What you see. The starting point for addressing any equine health related issue is your observation.


Underbite, Lower Jaw Protrudes Forward (in Adult)


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 in miniature breeds), or from injury or trauma to the lower jaw. An undershot is a situation in which the nipping teeth dont meet but the cheek teeth do. A true underbite involves abnormal occlusion of the cheek teeth too, and the development of overgrowth of unopposed teeth.

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.

  • 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.

your role


What To Do

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's role

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.
Questions Your Vet Might Ask:
  • Does the horse have difficulty chewing or eating?
  • What is the age and breed of the horse?
  • Do you notice any other problems with the horse?
  • What are the results of the Whole Horse Exam (WHE)?

further reading & resources

Author: Doug Thal DVM Dipl. ABVP