Dude i have hunted deer for 21 years and i have never known they had blood in there antlers
Elk antlers actually have a lot of blood in them. Their antlers when growing are actually porous and soft. When the antlers are soft they are known as velvet, and are harvested for different purposes. When they shed their velvet they become the antlers that are dense and rugged, but still maintain that porous interior.
I got to harvest velvet when I was younger at my grandfathers ranch in Colorado, it was a great experience.