Winners mate with multiple females and losers fail to mate. In white-tailed deer, only males have antlers, and they have them only in the mating season. Males fight for females by locking antlers and shoving. Like mountain-goat males, winning male dear mate with multiple females and losers don't mate. Unlike mountain goats, male deer shed their antlers in the winter as soon as the mating season is over.
Antlers regrow in summer and are fully grown by the fall mating season.
If attacked by predators, males with antlers will defend themselves by kicking and by striking with their antlers. Females and males without antlers kick to defend against predators. Give an example. Note that this example is a bit unusual because usually stronger males win more fights, so get more mates and more offspring. But there are organisms where weak males who avoid fights are successful at getting mates by sneaking copulations.