Determining Age of Horses by Their Teeth

Wayne Loch and Melvin Bradley, Department of Animal Sciences, University of Missouri-Columbia


The art of determining the age of horses by inspection of the teeth is an old one. It can be developed to a considerable degree of accuracy in determining the age of young horses. The probability of error increases as age advances and becomes a guess after the horse reaches 10 to 14 years of age. Stabled animals tend to appear younger than they are, whereas those grazing sandy areas, such as range horses, appear relatively old because of wear on the teeth.

Horses, like people, vary considerably in vigor and longevity. In general, they have passed their physical peak when they reach 9 to 10 years of age. At this age, the chance of an unsoundness being present has increased.

Age determination is made by a study of the 12 front teeth, called incisors. The two central pairs both above and below are called centers, pincers, or nippers. The four teeth adjacent to these two pairs are called intermediates, and the outer four teeth are designated as corners.

Canine teeth or "tusks" may appear midway between the incisors and molars at 4 or 5 years of age in the case of geldings or stallions, but seldom appear in mares. Adult horses have 24 molar teeth.

There are four major ways to estimate age of horses by appearance of their teeth: (a) occurrence of permanent teeth, (b) disappearance of cups, (c) angle of incidence, and (d) shape of the surface of the teeth.

Occurrence of permanent teeth
Horses have two sets of teeth, one temporary and one permanent. Temporary teeth may also be called "baby" or "milk teeth." Temporary incisors tend to erupt in pairs at 8 days, 8 weeks, and 8 months of age.

A well-grown 2-year-old may be mistaken for an older horse unless permanent teeth can be accurately identified. Permanent teeth are larger, longer, darker in color, and do not have the well-defined neck joining root and gum that temporary teeth do.

The four center permanent teeth appear (two above and two below) as the animal approaches 3 years of age, the intermediates at 4, and the corners at 5. This constitutes a "full mouth."

Disappearance of cups
Young permanent teeth have deep indentures in the center of their surfaces, referred to as cups. Cups are commonly used as reference points in age determination. Those in the upper teeth are deeper than the ones below, hence they do not wear evenly with the surface or become "smooth" at equal periods of time. In general, the cups become smooth in the lower centers, intermediates, corners, upper centers, intermediates, and corners at 6, 7, 8, 9, 10, and 11 years of age, respectively. A "smooth mouth" theoretically appears at 11. A few horse owners ignore cups in the upper teeth and consider a 9-year-old horse smooth-mouthed. Although complete accuracy cannot be ensured from studying cups, this method is second in accuracy only to the appearance of permanent teeth in determining age.

As cups disappear, dental stars appear first as narrow, yellow lines in front of the central enamel ring, then as dark circles near the center of the tooth in advanced age.

Angle of incidence
The angle formed by the meeting of the upper and lower incisor teeth (profile view) affords an indication of age. This angle of incidence or "contact" changes from approximately 160 to 180 degrees in young horses, to less than a right angle as the incisors appear to slant forward and outward with aging. As the slant increases, the surfaces of the lower corner teeth do not wear clear to the back margin of the uppers so that a dovetail, notch, or hook is formed on the upper corners at 7 years of age. It may disappear in a year or two, reappear around 12 to 15 years, and disappear again thereafter. The condition varies considerably between individuals, but most horses have a well-developed notch at 7.

Shape of the surface of the teeth The teeth undergo substantial change in shape during wear and aging. The teeth appear broad and flat in young horses. They may be twice as wide (side to side) as they are deep (front to rear). This condition reverses itself in horses that reach or pass 20 years. From about 8 to 12 years the back (inside) surfaces become oval, then triangular at about 15 years. Twenty-year-old teeth may be twice as deep from front to rear as they are wide.

Abnormal teeth conditions
"Parrot mouth" is a result of the upper and lower incisors not meeting because the lower jaw is too short. This condition is rather common and may seriously interfere with grazing.

"Monkey mouth" is the opposite of parrot mouth and is seldom seen in horses.

"Cribbing" is a habit common to stabled horses which damages incisors by chipping or breaking them.

"Bishoping" is tampering with cups to make the horse appear younger than it is.

"Floating" is filing high spots in molars to facilitate chewing. Molars should be checked regularly by veterinarians as the horse approaches mid-life and should be kept floated as needed thereafter.

Definition: "Galvayne's Groove." A groove said to appear at the gum margin of the upper corner incisor at about 10 years of age extends halfway down the tooth at 15 years and reaches the table margin at 20 years. It then is said to recede and disappear at 30 years.

Reprinted with permission from Department of Animal Sciences, University of Missouri
2004-2012 Horse Tack Review



 Horse Tack Reviews
 Submit Your Own Review!
 Search Review Database
 All Reader Reviews
 Staff Reviews
 Submit a Product for Review

 English Tack Reviews
 Dressage Saddles
 Jumping Saddles
 Close Contact Saddles
 All Purpose Saddles
 English Saddle Fittings/Pads
 English Bridles
 English Bridle Accessories
 English Show Apparel
 English Casual Apparel
 English Chaps/Boots/Helmets
 English Miscellaneous

 Western Tack Reviews
 Barrel Saddles
 Reining Saddles
 Roping Saddles
 Show Saddles
 Trail Saddles
 Western Saddle Fittings/Pads
 Western Bridles
 Western Bridle Accessories
 Western Show Apparel
 Western Casual Apparel
 Western Chaps/Boots/Hats
 Western Miscellaneous

 Horse Gear Reviews
 Horse Boots and Wraps
 Halters/Ropes/Leads
 Horse Health and Well Being
 Horse Apparel
 Horse Treats
 Horse Miscellaneous

 Barn & Stable Reviews
 Fly Control
 Gifts/Books/Videos
 Grooming Equipment
 Stable Accessories
 Tack Room
 Training Equipment
 Barn and Stable Misc

 Articles
 Barn and Stable Articles
 English Articles
 Feature and Misc Articles
 Grooming Articles
 Horse Care & Health Articles
 Horse Related Gift Articles
 News and Events
 Training Articles
 Western Articles

 Other Features
 About Us / Contact Information
 Articles & Subjects By Date
 Article Archives
 Join Our Mailing List
 Privacy Policy