What are antlers made of?

Antlers are the large bony appendages found on the heads of most male deer species. They start life as spongy tissue which gathers minerals and becomes hard bone. The spongy tissue and then bone are covered by a layer of skin called velvet, providing blood to deliver oxygen and nutrients to the antlers. Once an antler has grown to its full size, the velvet falls or is rubbed off and the bone dies, forming the mature antler. This mature antler will eventually fall or be broken off and be regrown each year. Antlers are different from horns, which are made of keratin layered over bone and grow continuously.