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Aging horses by their teeth

Horse Health: System is more of a guideline than an absolute determination

In 1885, Sydney Galvayne published a book in Glasgow outlining a system which claimed to accurately age horses by identifying distinct features of wear on the teeth.

Galvayne’s treatise became widely accepted and uncontested amongst horsemen for over a century. The Galvayne name even became memorialized when a distinct groove which travels down the side of the corner upper incisors was aptly named Galvayne’s Groove.

This yellow-brown groove was said to appear at the gum line of the upper corner incisors at the age of 10 and would lengthen as the horse aged. It would span the entire tooth by the age of 20, then leave the gum line and advance toward the bottom of the tooth until it wore out at age 30.

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Recently Galvayne’s treatise was taken to the test by the scientific world where the century-old system was discovered to hardly be the science that we once were led to believe, and that the practise of aging horses using dental characteristics has a degree of uncertainty.

Researchers in Britain and Belgium compared the traditional marking system as outlined by Galvayne against the horse’s accurately known date of birth and/or true age as recorded in the horse’s registration papers.

The researchers discovered surprisingly significant discrepancies in their comparisons, placing the reliability of a century-old practice for aging horses by their dentition under marked scrutiny. The studies showed that specific ages could not be assigned to individual horses according to the dental criteria outlined by Galvayne’s treatise due to the tremendous variation amongst individuals.

Researchers found there to be no consistency in dental traits amongst horses within specified age groups and that horses showed marked variability from the “textbook” findings.

Knowing the age of a horse can be important for a number of reasons. Not only does age determine the dollar value of a horse in horse-related transactions, age also determines what type of handling and care the horse will receive. Although registration of horses is a common practice today, there exists a surprising number of horses without a paper trail identifying their date of birth.

As a result, veterinarians are commonly called upon to identify the age of a horse. For example a 10-year-old gelding will be a better riding investment than a 20-year-old gelding, a two-year-old will require different handling than a four-year-old, and a six-year-old brood mare has more foaling potential than a 16-year-old mare.

Without argument, significant changes do occur in the teeth of horses as they pass through time. Dental maturation of the horse progresses over a five-year period taking the horse from toothless at birth, through 24 baby teeth and ending with a count of between 36 and 42 permanent teeth.

Horses, just like human children, shed their baby/milk teeth at a highly predictable pace. Young horses lose their central incisors at 2-1/2 years, the ones next to the middle at 3-1/2 years and the corner incisors at 4-1/2 years. Due to the timely nature of tooth shedding and eruption a strong correlation exists and the age of horses by inspection of the teeth can be developed to a considerable degree of accuracy when identifying horses under five years of age.

As the horse ages beyond five years, errors in judgment tend to increase as a number of variables play a role in how the horse’s teeth age, thus making it more difficult to specifically age the horse. For example, breeds such as the Arabians are known to have slower wear patterns than draft horses due to the increased hardness of their enamel, thus presenting their mouths to be more youthful than they actually are. Other variables affecting tooth wear include diet, grazing conditions, management practices, vices, and more recently, dental work. The probability of error increases as age advances and becomes an informed guess as the horse enters its late teens and 20s.

Good reliability exists when distinguishing the difference between a six-year-old horse and a 16-year-old horse. However, correctly identifying whether a horse is 15 or 16 years of age is not too likely. Galvayne’s system for assigning dental features to specific ages of horses offers more of a guideline than an absolute for age determination.

About the author

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Carol Shwetz is a veterinarian focusing on equine practice in Millarville, Alberta.

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