Nine Books on the Nature of Things

The same signator marks a stag’s antlers with branches from which its age is known: the stag is as many years old as the antler has branches. Since one new branch is added each year, its age can be recognised up to twenty or thirty years. The signator also marks a cow’s horns with rings, from which the number of calves she has carried is known, each ring indicating one calf. The same signator pushes out a horse’s first teeth so that its age can be known certainly from them in its first seven years. Fourteen teeth first grow in a newborn horse, of which it loses two each year, so that all fall out over seven years. For this reason a horse older than seven can be judged only by someone highly skilled and practised.