Last week we learned husbands have birthdays and hounds have human age equivalents. But what about horses? Unlike purebred dogs, most horses don’t come with registration papers with their birthday proudly displayed, so it’s a guessing game. Even Thoroughbreds registered with The Jockey Club lose their actual birthdays to the convenient New Year’s Day in order to have a consistent racing year.
Before you can calculate a horse’s human age equivalents, you have to determine the horse’s age in actual years. For centuries horse traders have peered into the equine mouth to look for clues. Horses, like dogs and humans, have two sets of teeth, their baby or ‘milk teeth’ and their permanent teeth. Most horses have all their permanent teeth by age 5 and are considered to have a ‘full mouth.’
It’s easy to look at a very young horse’s mouth and see which milk teeth have appeared or been replaced by permanent teeth in determining his age. Once a horse is considered ‘aged’ (9-years-old and beyond) there are other more subtle signs to look for. Unlike dogs and humans, horse’s permanent teeth continue to grow throughout their life. This phenomena ensure a lifetime of grass grazing and grain grinding. As they age, horse teeth also change shape and develop markings.
Cups, Stars, Grooves, and Hooks
Cups: The shape of the tooth changes from rectangular to triangular as the horse ages. When you open the mouth of a young horse and view the bottom front teeth (center and corner incisors) on the grinding surface from above, you will see dark rectangular centers called ‘cups.’ These cups are visible on all incisors by age 5, but slowly disappear from the teeth progressively. They fade first on the bottom from the center teeth out to the corners and then on the top from the center out to the corners, so by age 11 all the cups should be gone.
Stars: As the cups begin to disappear, a ‘dental star’ appears on the grinding surface towards the front of the tooth. This yellow-colored spot starts out rectangular and becomes rounded with age and will eventually replace the cup on each incisor. The stars begin to show up around age 8 on the center teeth and appear on the corners by age 11.
Galvayne’s Groove: This dark-colored groove is located on the incisors at the upper corner of the mouth, just before the canine teeth. This groove won’t appear until the horse is around 10 years old. It appears first at the top of the tooth and works it way down the front of the tooth. It reaches the middle of the tooth by age 15. Then it continues down to the bottom of the tooth by age 20. Then it reverses itself and starts to disappear from the top of the tooth, so by age 25 it’s only visible on the lower portion of the tooth. By age 30 it should have disappeared from the tooth.
Hooks: Another clue to determining age can be looking for hooks on the top corner incisors. Uneven wear on the upper and lower corner incisors can cause a hook to form at the back and bottom on the top corner incisor. The first hook appears at age 7 and disappears at age 9. Then it re-appears at age 11 and remains until the mid-teens.
Another indicator of age can be seen by viewing the horse’s mouth in profile. Lifting the lip take a look at his bite from the side, the older the horse, the longer and more angled forward his permanent teeth will be. For you trivia buffs out there, the term “long in the tooth” comes from the horse world and refers to this observation. This term also gave birth to a piece of sound advice: “Don’t look a gift horse in the mouth!”
Horse Age in Human Years
Is there an equivalent human age for horses? It appears about a decade ago, as part of a marketing campaign from Pfizer Animal Health (now Zoetis) to promote their Strongid daily wormer, they released The Age Relationship Chart which calculates a horse’s age in human years. A rough estimate said that horses are basically 6.5 years old when they are born (because when they are born they can stand and run) and will age that fast (in human years) until they reach four. After that they settle into a 2.5 human years for every actual horse year for the rest of his life.
According to the 2003 press release from Equine Resources International, LLC, “Horses go through the same life cycles as do humans. They have distinct childhood, adolescence, puberty, maturity and geriatric phases of their lives,” said Dan Kramer, Pfizer’s equine market manager. “This chart will give horse owners added insight into their horse’s life stages and greater understanding of the issues at each stage. For example, a 22-year old horse would equate to a human of age 65.5. A horse that is 36 years old would be celebrating its 100th birthday if it was a person.”