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By M.T. Martin, W.L. Scrutchfield, J.R. Joyce, Matthew Martin

Aging horses by their incisor teeth is as much as art as a science. Traditional "indicators of age" such as eruption date, "cups," Galvayne's groove, hooks, shape of the table surface of the lower central incisors, etc. often result in wide age estimates. The authors believe that accuracy can be improved by first placing horses less than 20 years old into one of four age groups before applying the traditional indicator. Then by using a systematic approach and applying the following concepts, the age of most horses can be accurately estimated.

Important Concepts:

1. Horses under 20 are placed into one of four age groups by examining a single tooth, the upper corner incisor (UCI).

2. All traditional "indicators of age" can be used but eruption dates, "cups," Galvayne's groove and the table surface shape of the lower central incisors are most reliable.

3. When examining horses under five years the examiners should be aware that time of year is very important. For example, a three year old’s teeth will look much different in February than they will in November.

4. Most horses are born in the spring and all have a birthday on January 1.

5. "Atypical" horses do occur and can usually be recognized when their age group and indicators do not match, resulting in wide age range estimates.

Age Categories:

Under five - This age group has a deciduous (baby) UCI from 8 months to 4 _ years. Eruption time of the central, middle and corner incisors (2 _, 3 _, 4 _ years) are the primary source of information in this age group and are considered highly accurate in the general population.

Five to nine - UCI is now a permanent tooth and should be wider than it is tall (5-6 years) progressing toward square (9-10 years). Younger horses in this age group should have "cups" on the table surface of the lower incisors. These cups will be gone from the central incisors once the horse turns six years old, gone from the middle incisors by age seven and gone from the corner incisors at the age of eight or nine. The table surface of the lower central incisor should be oval from side-to-side in this age group.

Ten to fourteen - The UCI should be square (9-10 years) to taller than wide (12-14 years). Galvayne's groove should start to appear at the gum line when the horse is 10 years old and progress to halfway down the UCI by the age of 15. The table surface of the lower central incisor should be round to triangular.

Fifteen to twenty - UCI should definitely taller than wide thus the saying "long in the tooth." Galvayne's groove will usually be halfway (15 years) to all the way down the UCI (19-20 years). The central incisors are significantly smaller than the middle incisors and the lower central incisor table surface should be oval from front to back.

As horse's approach the age of 20, the accuracy of estimating their age decreases. Breed differences can also occur. The best advice when learning to age horses is to look at horses of known age within a breed and use a systematic approach such as the one described above.

Authors M.T. Martin and W.L. Scrutchfield are Equine Field Service Clinicians and J.R. Joyce is a Community Practice Clinician at Texas A&M University.