A few years back my wife and I were on a flight and noticed a young girl sitting across the aisle. She was very chatty and had an incredible smile. Later I asked Bonnie how old she thought the girl was. Without hesitation she said, “Eight”. I asked her how she knew that. I hadn’t remembered it coming up in our conversation with the youngster. She said, “That’s easy, I could tell by her teeth.” Her teeth? You have to understand that for many years Bonnie taught second grade. Every day she would see the mouths of the children in her school. Without even trying to she learned that the children in her grade were losing baby teeth and getting adult teeth in a very predictable way. I got a big kick out of the whole episode because I am often asked to “age” a horse. I had never given any thought to having this work with kids.
So, how accurate is aging a horse by his teeth? Actually, up to the time that a horse is 8 this is a pretty good measure of age. After that, age estimation isn’t as accurate because it depends somewhat on a horse’s diet and the anatomy of each horse’s skull and jaw. As they become teenagers it is really more of an art than a science, and even two experts can differ by 2 or 3 years on just how old a certain horse is.
Here are the fundamentals from 3 to 8 years old that, with some practice, can make you a pretty good estimator. First of all, the teeth to focus on are the incisors. If you are going to be bitten by a horse, it’s the incisors that will get you. Gently roll your horse’s upper and lower lip back and you will see 12 incisors, six uppers and six lowers. Both lower and upper incisors come in pairs. There are the central two, the intermediate or middle two, and the corner two, top and bottom. When a horse reaches his third (actual) birthday, the permanent centrals will have come in. These 4 permanent or adult teeth will be quite a bit bigger than the intermediate and corner baby teeth. By the 4th birthday the four intermediates will have erupted. Now the incisors will show 4 large adult teeth and the tiny baby teeth on the corners. At 5 years the horse will have a “full mouth”, which means that all of the incisors will be the larger permanent teeth. It’s that easy: Right about the 3rd, 4th, and then 5th birthdays the centers, middles and corners become adult teeth.
There is also something that happens right around the 6, 7 and 8 year birthdays. Focus just on the bottom jaw, and look at those incisors. Right on the flat, biting surfaces look for a dark oblong depression, or “cup” right in the middle of each. Just as the teeth erupt at definite times, the cups disappear on a timetable. At 6 years, the center cup disappears, at 7 the middle cup, and at 8 the cups are gone from all the incisors. So the time table is 3, 4, and 5 years for eruption of the permanent teeth, and 6, 7, and 8 years old for the cups to leave.
If this is of interest to you, start learning this skill by checking horses in the barn whose age you know, and then see if what you are seeing checks out. It’s a great skill, and with a little practice will be yours.
– David A. Jefferson, D.V.M