Being able to age within a fairly narrow range can be useful for owners of unregistered horses or horses whose age is unknown for some reason. Many health and nutrition management decisions are directly related to age and dental wear, making it even more important that all horse owners have a general understanding of how a horse’s mouth changes with age. From a historical perspective, until recently, when organized associations began keeping registered horse birth dates, most horse professionals prided themselves on their ability to determine age by examining any horse’s teeth. horse. Determining the age of the horse from the teeth is not an exact science, but changes do occur that can help determine the approximate age, and anyone can learn the basics.
To use as a reference guide, figures 1 and 2 indicate the names of the teeth.
Reading: 30 year old horse teeth
Horses under the age of 5 go through very typical dental changes. With foals, a good rule of thumb to remember is that their baby teeth, or deciduous teeth, erupt, or erupt, following a simple 8-day, 8-week, and 8-month schedule. Is that how it works. foals are born without teeth or with four central incisors, two above and two below. if the central incisors are not present at birth, they usually erupt within 8 days. the intermediate incisors erupt at 8 weeks (figure 3) and the corner incisors at 8 months. these are deciduous or temporary milk teeth that will be lost as the young horse ages. deciduous teeth can be distinguished from permanent teeth because they are wider than they are tall and have shallow roots. twelve premolars will also erupt within 2 weeks of age, three on each side of the upper and lower jaws. however, premolars are generally not used in older horses, as they are more difficult to see.
Other dental changes occur in annual increments, and the young horse’s mouth changes like a child’s when it loses its deciduous teeth. this systematic shedding of deciduous teeth is what we use to “age” horses until they have all their permanent teeth at 5 years of age.
pattern of deciduous teeth
At 2½ years, the horse’s primary central incisors recede as the permanent central incisors erupt from below (figures 4 and 5). by age 3, the upper and lower central incisors have grown enough to join together and therefore begin to grind against each other. this is known as being “in use”. these wear patterns will be used later in the horse’s life to help determine age. at 3 and a half years the intermediate incisors will have fallen out and at 4 years they will be worn. at 4 ½ years the corner incisors will have fallen out, and at 6 months they will be worn. see table 1 for a list of dental changes.
table 1. mean ages of dental eruption in horses
credit: horse chart by j. Warren Evans
Male horses have four canine teeth (tushes) located between the corner incisor and molars. mares will occasionally have canines, but usually these are not as developed and all four may not be present. these teeth appear during the horse’s 4-year-old year. they should not be confused with wolf teeth which have very shallow roots and lie adjacent to the first premolar.
Wolf teeth are often removed, as they can interfere with biting. canine teeth are not extracted under normal circumstances. (See the Utah State University Extension fact sheet on equine dental care for more information on dental care.) p>
other factors to determine age
Once all the permanent teeth are present, other indicators help determine age.
on the polished surface of the incisors, a cup is seen as a jagged area with a dark center in the middle of each tooth. the cups disappear from the lower central incisors at 6 years, the intermediate ones at 7 years, and the corners at 8 years. the upper incisors lose their cups from the center to the corners at 9, 10, and 11 years of age, respectively. the term “smooth-mouthed horse” applies to a horse 12 years of age or older when all the tops are gone and the grinding surface is smooth (figures 6a and 6b).
The next thing that appears on the polished surface of the incisors is a dental star or a yellowish stain. it appears more towards the front of the teeth (closer to the lips) than the cups (figure 6a). At first this star appears rectangular, but as the horse ages it becomes more rounded and moves towards the center of the tooth. the dental star will appear in the central incisors at 8 years, the intermediate ones at 9 years, and the corners at 10 years.
The shape of the grinding surface, the number of teeth visible below the gum line, and the angle of the teeth change with age. a horse under the age of 9 will have a rectangular crushing surface, a 9-year-old horse in its mid-teens will have a more rounded crushing surface, while a horse in its late teens or older will have a triangular surface (figures 7a and b).
The younger horse will show a shorter tooth visible below the gum line, while the term used for the older horse is “long tooth” because the tooth is more visible. when viewed from the side with lips parted, the young horse will exhibit a more upright alignment of the incisors, while an older horse will be more angled with a more protruding appearance (figures 8a and 8b).
A more subtle indicator that can help with aging in the 10+ year horse is the galvayne groove (figure 9). this is a groove that appears near the gum line of the corner incisor. it begins in the center of the outer surface of the tooth in a 10-year-old child. at age 15 the groove extends to the middle of the tooth; at age 20 it extends over the entire length of the tooth; by the age of 25, the upper half of the groove disappears, so a groove appears only in the lower half; and by age 30 the groove is completely gone.
Another subtle indicator on the same corner tooth is the 7 and 11 hook. As the mouth changes shape, the backs of the upper and lower corner incisors may not meet, allowing a hook to form on the upper incisor (Figure 10). the first time this hook appears is at 7 years old and it will disappear at 9 years old. it will reappear at 11 years of age and may remain until the mid-teens.
These guidelines for aging due to dental wear can vary depending on what the horse is eating and what vices it is. For example, breeding horses can wear down the upper incisors, interfering with normal tooth wear. while not all horses follow the rules, these guidelines can be useful tools in assessing a horse’s age.
- Jeffrey, D. (nineteen ninety six). Equine dentistry, the theory and practice of equine dental maintenance. norfolk printing co.
- evans, jw. (1981). horses. san francisco: w. h. free man and company.
revised May 2020utah state university extension peer reviewed fact sheet
Reviewed by Karl Hoopes, DVM, Equine Extension Specialist, Utah State University Originally written by Patricia A. evans, ph.d., and nancy jack, ph.d.