When Karen came home with a new horse that she just bought, she had a friend take a good look at his teeth. She had been told he was going on five, but the friend said his teeth looked closer to that of a two-year-old. When the veterinarian confirmed through overall examination that he was indeed much closer to two, Karen turned the horse out to pasture to mature for a year or two before starting him under saddle.
Aging a horse by his teeth is not a foolproof method; however, you can guesstimate within a few years. At least you can tell a horse younger than 6 from a 15-year-old horse. Why can one age a horse by his teeth? Because teeth change throughout the life of a horse. In fact, his teeth will continue to grow to about 25 or 30 years old.
The incisors are the teeth used to determine age range, and there are three pairs of incisors on the upper jaw and three pairs on the lower jaw. For young horses, the first incisors that grow are temporary and fall out to be replaced by permanent ones between two and three years old. These incisors in a young horse are small and close to square-shaped; whereas in older horses, incisors are more rectangular, growing longer more than wide.
The baby incisors fall out in particular order: the center pair at around 2 ½; the pair next to them at about 3 ½ and the pair beyond at around 4 ½.
All permanent teeth are usually in by age 5.
At around 6 years old, the first signs of a “7-year hook” become apparent. That’s when a notch appears at the bottom of the top corner incisors. The hook appears at the bottom corner of the upper corner incisor.
It becomes more apparent as the lower incisor is more narrow and fits into the notch, but it usually wears away after 8.
The middle groove, called Galvayne’s groove, starts around age 10 and grows down as the tooth grows until reaching the bottom at around age 20.
The slope and angle of the incisors also change with age; the top and bottom incisors start at about 160 degrees and then decrease until about 80 degrees when the horse is 20. In other words, as the horse gets older, the teeth slope more toward the front.
Wear patterns can also help assess age. On the grinding surface of the teeth is a dark cup that wears so that the pulp becomes exposed. The pulp appearance is called the “dental star.” The dental star changes shape as the horse ages, going from a line shape to oval shaped then to round.
Also, the teeth of a young horse change shape from oval to round and finally triangular.
Though aging by teeth can’t give you a definite age, you can assess a range. An overall examination by a veterinarian that accounts for the horse’s condition, the hollows above his eyes, white hairs in the face, wear on the limbs and joints or dipping of the back can give you a better idea of just how long in the tooth he really is.
