An estimation of a horse’s age by examining its teeth is just that, a
guesstimation.
The changes that occur in horses’ teeth through their lifespan have
been documented as long ago as 600 BC by the Chinese and by the ancient
Greeks and Romans. Much documentation has accumulated since then.
Repeating themes and commonalities appear, but no absolutes. In fact,
indicators of age are deemed inaccurate when scientifically scrutinized.
Horse teeth, unlike the teeth of humans and many other animals,
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continue to erupt and grow throughout the animal’s life.
The main criteria when determining a horse’s age by its teeth are
eruption dates and appearance of the tooth’s occlusal surfaces, which
are the grinding surfaces, or the parts of the tooth that come into
contact with its opposing tooth.
Eruption date, which is when the tooth breaks through the gums, tends
to be more accurate than wear pattern, but is obviously limited to
younger animals.
Age estimating becomes more speculative with increasing age because
lifestyles, environmental influences, diet and breed directly affect
the rate and manner in which teeth wear down.
The most appropriate teeth for estimating age are the incisors because
they are the most accessible for inspection. These are the front teeth
used for nipping forages, with six on the top and six on the bottom.
From inside to outside on the centre line, the incisors are called
central, intermediate and corner. Baby teeth, or deciduous incisors,
are smaller, whiter and usually more triangular than their adult
counterparts, which tend to be larger, more yellow and rectangular.
Eruption times for foals of the central, intermediate and corner
incisors are about six days, six weeks and six months respectively.
Eruption times of the central, intermediate and corner adult incisors
are 2.5, 3.5 and 4.5 years respectively.
Therefore, estimating the age of horses younger than five years can be
considered fairly accurate.
Horses between five and nine years old have an upper corner incisor
that progresses from being wider than it is tall to being square. The
upper central incisors should be taller and wider than the intermediate
incisors when viewed from the front.
The side view of the incisors where the upper and lower incisors meet
should be almost 180 degrees. This angle becomes sharper with age. The
teeth protrude toward the front, hence the saying an old horse is “long
of tooth.”
Horses between 10 and 14 years old will have an upper corner incisor
that is square to slightly taller than wide in shape.
Galvayne’s groove, which is a shallow darkened groove on the outside
surface of the upper corner incisor running up and down, should become
evident, but should be no farther than halfway down this tooth. As the
horse approaches the upper limit of this age group, the central
incisors usually begin to appear the same size or smaller than the
intermediate incisors from the front.
The occlusal surface of the lower central incisor should begin to
resemble a triangle and the incisor profile angle should begin to
change toward a more acute angle.
Horses between 15 and 20 years old have an upper corner incisor that is
taller than it is wide. The Galvayne’s groove should be midway to all
the way down the tooth. The incisor profile in the upper limit of this
group should be significantly acute. The upper central incisors
commonly are much smaller than the intermediate incisors when viewed
from the front.
It is within the criteria of this age group that the finer tuning of
hooks, cups, dental stars, enamel rings, and grooves can be applied.
Using several criteria, a person can refine the ability to provide an
informed guess about a horse’s age.
Carol Schwetz is a veterinarian practising in Westlock, Alta.
