Ten Years Old

Some horses start to grow a Galvayne's groove at around 10 years old. This is a groove that appears at the top of the upper corner incisors and begins to grow downward.

Eleven to Thirteen Years Old
A pronounced hook sometimes appears on the corner incisors, which should not be mistaken for the hook that appears at seven years old.

This larger hook usually remains on the teeth and does not disappear, as in the earlier case.