A putto is often called a cherub (plural cherubs) although unlike the Biblical cherub (plural cherubim) in form and symbolism: cherubim have four faces of different species and several pairs of wings, and are sacred, whereas putti are secular and represent a non-religious passion.
(The term stallion for an uncastrated male horse dates from this time; stallion = stalled one.) Stallion is also used to refer to males of other equids, including zebras and donkeys.
Mares can be covered, however the important factor of sperm/ejaculation is the overriding determiner of fertility. If the young stallion is used frequently, there will not be enough sperm available per ejaculation and his rate for settling mares will be sub-standard.