Mature, intact male cattle that are used for breeding cows and heifers are called bulls. Intact male cattle that are almost, of or past weaning age but are younger than 2 years of age are called...
A bull calf or a yearling bull. You can also get steer calves, or weaner or feeder steers too, if the bull calf has been castrated.
A young tom cat or a tom kitten.
A shoat-boar if intact or a shoat-barrow if castrated.
A male horse that is not neutered is a stallion, a male horse that is neutered is a gelding. A male horse that is 4 or under is called a colt.