The horse has 24 upper and lower teeth on each side of its mouth. These are called incisors and they are most commonly used for estimating the age of a horse. It is also possible to use the horses cheek teeth as well, but they are harder to see and do not change significantly with time.
Up until the age of 5 a horse’s age can be estimated very accurately. This is because the emergence of the deciduous and permanent teeth follows a predictable time frame. After this, aging the horse becomes more difficult. It is however still very useful to be able to tell a horse’s approximate age. This can be very helpful for planning a dental care schedule and determining a horse’s nutrition needs as a function of age.
To examine a horse’s age, you will be focusing on the incisors (which are located in the front of the mouth). When a horse is young its incisors have a rounded and oval shape in cross section. As the horse ages its teeth wear and the occlusal surface of the incisors changes shape, first to a triangular shape and then a rectangular one. This also affects the angle at which the incisors meet and their shape.
There are several key features to look for that can help with aging a horse, these include: the angle at which the teeth meet; cups and dental stars; and the shape of the incisors. In addition a horse’s teeth have a long root that resides deep in the jaw bone. Over time, as a horse chews and grinds it erodes the peri-dental enamel. This shortens the tooth and brings about various marks and grooves on its chewing surface.
One of these markings is the so-called seven-year hook, which is a vertical brown mark on the front of the upper corner incisor. It appears around the age of seven, disappears a year later, and reappears at thirteen. Another mark is Galvayne’s groove, which is a vertical line that appears in the front of the upper incisor at about 10, and half down by 15, fully gone by 20 years old.
These key characteristics can be viewed during a routine oral exam, which should be included in every horse’s annual physical examination by your veterinarian. In addition to evaluating the horse’s overall health, these exams will help prevent dental disease and keep your horses looking their best.