Farm lesson for the day:
Both bulls and cows can have horns. Many breeds are "polled", which means they don't even develop horns. The polled condition is desirable for dairy and beef cattle so they can't hurt workers or each other, especially in close quarters. Since the gene for horns is recessive, it is hard to stamp out because polled animals can carry the horned gene. If a calf (male or female) gets "horn genes" from both parents, it will grow horns.
Some cattle, such as Longhorns and the bulls used for bullfights and rodeos are bred to have horns because they look bad*ss.