Icelandic horse study: How accurately can age be estimated from their teeth?

Icelandic Horses in Iceland.
Icelandic Horses in their native Iceland. © Nick Hodgson

Using the state of the teeth to judge the age of horses has been used for centuries, but how accurate is it for the Icelandic breed?

Jarosław Łuszczyński and his colleagues, writing in the journal Animals, note that age estimates for horses based on the appearance of teeth seem to suffer from relatively large errors.

That said, it can be useful in identifying the age of horses of unknown origin, and can help owners, breeders, or veterinary surgeons to make decisions regarding purchase, insurance, or treatment.

The researchers undertook a study to assess the age of Icelandic horses based on the state of their teeth, in particular selected features of the incisors.

They used 126 Icelandic horses ranging from foals to 24-year-olds for their study. They all lived on a stud farm in southwestern Poland.

The assessments were performed by an experienced horse person with extensive experience in determining age based on the appearance of the teeth, but with no specialization in veterinary equine dentistry.

Age was determined based on the inspection of the teeth and compared to the actual age of the horse recorded in the equine passport.

The estimated age did not match the real age in 36.5% of the horses.

Age was more often underestimated (19.0%) by, on average, 0.9 ± 1.0 years than overestimated (17.5%) by, on average, 1.3 ± 1.4 years.

The least number of errors in determining age were made in young horses aged 0–2 years, when the eruption and growing of the deciduous incisors (milk teeth) and the disappearance of the cups was considered.

The average percentage of errors in this group (2.1%) was significantly lower than for older horses, whose age was estimated based on the exchange of milk teeth to permanent teeth (55.8%), the disappearance of the cups (68.0%), and shape changes on the grinding surfaces (40.0%).

“Significantly more frequent underestimation of age based on replacing deciduous for permanent incisors and significantly more frequent overestimation of age on the basis of the disappearance of the cup may indicate that Icelandic horses up to five years of age are characterized by a slower rate of growth than horses of other breeds, especially warmblood horses,” they reported.

“It is likely that characteristic changes occurring in Icelandic horses’ incisors may be related to the specific course of development processes of this breed.

“These results suggest that patterns used to determine the real age of horses based on changes occurring on the incisors should be modified in order to consider the specificity of the course of growth and maturation processes of horses of various types and breeds.”

The authors suggest that slower abrasion of teeth of Icelandic horses might be a characteristic feature of primitive horses. Diet may also influence the abrasion of incisors.

The Frequency of Errors in Determining Age Based on Selected Features of the Incisors of Icelandic Horses
Jarosław Łuszczyński, Magdalena Pieszka, Weronika Petrych and Monika Stefaniuk-Szmukier
Animals 2019, 9(6), 298;

The study, published under a Creative Commons License, can be read here

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