Original: The terms for the male of a given animal species (stallion, bull, rooster, etc.) usually imply that the animal is entireâ "that is, not castratedâ" and therefore capable of siring offspring.
Simplified: The terms for the male of a given animal species (stallion, bull, rooster, etc.) usually mean that the animal is entire, that is, not castrated, and therefore capable of standing at stud.