Instructions
Check to see if the last molar has erupted. If the last molar has erupted the horse is at least 5 years old. Premolars are present at birth and are replaced by the first permanent molars at 2 1/2 years of age. At 3, the second molar erupts and between 3 and 4 years the third premolar.
Look at the wear on the chewing surface, or cups, of the lower incisors. The cups are the dentine-filled ovals in the center of the teeth, that are surrounded by enamel. Starting at three years of age the cups will start to wear down approximately two millimeters per year. By age 6, the cups of the lower central incisors will be completely ground away leaving nothing but a dark spot on the tooth called a mark. By 7, the cups of the lower intermediate incisors will be worn away, and by 8, the cups on the lower corner incisors.
Compare the wear on the cups of the lower incisors to the wear on the cups of upper incisors. Since the upper jaw is movable, the contact on the wearing surface is less and the cups of the upper incisors are ground down at a slightly slower pace. The cups on the upper central incisors will be completely ground away around 9 years of age instead of 6. The intermediate incisors' cups will be gone around ten years of age, and the corner incisors at eleven years.
Evaluate the shape of the chewing surface of the incisor as it will also change with age. The incisors are diagonally oval until around 12 years of age, then between 13 and 18 years they begin to change to a rounder form. Then between 18 and 23 the incisors become more triangularly shaped. Finally after the age of 23, they become more vertically oval.
Inspect the upper corner incisors for hooks or deep indentions in the chewing surface. At age 7, the position of the corner incisors will begin to shift, moving forward and into a more horizontal position. Once this shift occurs only 50 percent of the upper corner incisors' chewing surface will make contact with the lower corner incisors. This will cause hooks to appear around 9 years of age. The hooks will then disappear around 12 years, when the tooth shifts again. Some movement will occur again around 15 years and second hooks will appear; only to disappear again around 18 years of age. A third hook can appear around 20 years.
Look at the position of the incisors in relationship to each other. When viewing a profile of the incisors in a young horse, the upper and lower incisors almost form a straight line. The incisors will rest almost perpendicular to each other until 9 years of age, then the upper incisors will begin to angle, moving much faster then the lower incisors. At 15 years of age the upper and lower incisors will catch up and protrusion begins. As the horse ages the angle becomes more acute, approaching 120 degrees at about 20 years.
Verify whether Galvayne's groove has appeared on the outer surface of the upper corner incisor. Named for it's discoverer, Sydney Galvayne, who traveled throughout Europe judging the ages of horses and selling his secrets to other horse enthusiast. The grove erupts from the gum line at age ten. It runs down the middle of the tooth and will be halfway down the upper corner incisor by age 15. By 20 years of age the groove will run the length of the tooth. At 25 years the groove will disappear from the top of the tooth and only be visible on the lower half. Horses older than 30 will only have a little groove visible on the chewing surface.
How to Tell a Horse's Age by its Teeth
Traditionally a horse's age has always been determined by looking at his teeth. Unscrupulous horse dealers would try and change a horse's teeth to disguise his true age. Modern advances in equine dentistry, breed associations and micro chipping have given horse buyers and breeders other, highly reliable resources for learning the true age of a horse. Nonetheless, being able to estimate a horse's age from his teeth is still a valuable skill. Read on to learn more.