I actually saw a TV show once on something similar to this. The game wardens actually took a sample from the deers antlers and tested it, to show what minerals, and trace elements were found in the antler. They then could trace the deer to see where these nutrients were found.

In this instance on this show, a guy shot a trophy buck in Wisconsin, and tried to have it scored or something in Michigan. Somewhere along the way, something went fishy, and they checked his deer out. They determined that certain minerals found in its antlers were only found in Winsconsin soils on the other side of this river, and not where he claims to have shot it in Michigan.