Increased testosterone levels in the blood of bulls and bucks cause closure of the blood vessels that have nourished the growing antlers, resulting in the dying and shedding of antler velvet. Each male cervid rubs his rack against pliant shrub stems and small trees in order to “rub out” the velvet and prepare hardened antlers for their function in affirming his social and sexual status. It might take as little as an hour or as much as two days.
All summer long, the astonishing growth of antler tissue was supported by the velvet – the fuzzy-looking skin covering that both nourished and protected the elongating antlers. Velvet is blood-engorged vascular skin that dies and sloughs off naturally when the fully developed antler bones mineralize and harden. Velvet antlers shine with copious amounts of scent-dispersing oily sebum, which is produced by sebaceous glands found at the base of each hair follicle.
From spring to late summer, males have been growing their antlers, which are actually bones. Antler osteoblasts are the fastest-multiplying cells of any mammalian tissue. In just five months, a bull moose can develop a massive appendage on his head, weighing as much as 60 pounds, with a spread of six feet. Antler elongation within the protective velvet can reach three-quarters of an inch per day for moose, one-quarter inch per day for a whitetail. (via northernwoodlands.org)
So, now that you know a little bit more about antler velvet, take a look at this video footage and watch a buck try and rub his antlers on a human: