Looking a Horse in the Mouth

The horse in the photo above is likely 6 or 7 years old.

Do you ever wonder what your veterinarian is looking at when he or she opens your horse’s mouth to the estimate its age? It is intricate, and can take years of practice to really get good, but that doesn’t mean that you cannot at least get a general idea of what to look for. Here are a few basic rules that you can follow to at least estimate an age range in a horse by oral examination.

1) Horses tend to object to having their lips pulled apart and mouths opened. For this reason, standing off to the side when you open the mouth will help you avoid being injured since they often try to throw their head up in the air when you open their lips.

2) As you curl up the upper lip, look for a tattoo. If the horse has one, it is simple to determine its age since The Jockey Club assigns a letter to each year that a horse is born. For instance, all thoroughbreds that race on the track born in 2006 have a tattoo that begins with the letter “J.”

Credit: The Jockey Club

3) Check for “baby” teeth (also called deciduous teeth.) They are caps that will eventually be replaced by permanent adult teeth. Horses will have them up until the age of 5. Sometimes you will see missing caps which can hone you in on an age range.

4) If you open the mouth and look down at the occlusal (table) surface of the lower incisors, they will have a characteristic shape. In general, horse incisor teeth progress through different shapes as the horse ages. Here is the progression:

– Oval (0 to 5 yr) to

– Round (5 to 9 yr) to

– Triangular (10-15) to

– Square (15 to 19)

5) When you look at the incisors from the side, the contour and angle between the top and bottom incisors will change over time so that it becomes more angled as the horse ages.

Tooth Angles by age

6) In the upper corner incisor, most horses will have a marker called the Galvayne’s Groove. Here is how it progresses over time:

• Appears at the gumline at 12 years

• ½ way down tooth at 15 years

• All the way down tooth at 20 years

7) Remember, the term “long in the tooth” refers to an aged animal. Therefore when examining the upper corner incisor, the overall length of the tooth can give you a general idea as to age range. Here are general rules:

• Between 5 and 9 years, the tooth is wider than it is tall

• From 9 to 10 it is perfectly square (equal height and width)

• Gets longer than it is wide from there

The upper corner incisor goes from wide to long as the horse ages

There are several more markers that the veterinarian examines to help hone in on an estimated age, but these are a good start to get you in the ballpark. Generally, it is difficult to age a horse past 23 years no matter who is looking, but the general shape and length of the incisors, as well as their angle and the presence of the Galvayne’s Groove can get us close to knowing “young,” “middle-aged” or “older.”

For more information, you may want to consider purchasing the American Association of Equine Practitioners Guide to Determining the Age of the Horse.