What age can a male horse mate with a female?

Young stallions (colts(males)) can start mating at about a year or before. He might try younger but is still to young, You can geld(castrate) a colt at aobut a year old.

Young mares (fillies)females)) have a more complicting reprocducting process so they come in season to mate anyware from a year old to 2 1/2 years old