Looks like a whitey to me. Just read an article about hydrids. Most muley/whitey fawns only live around six months. Other stand a high rate of predation due to the mixed emotions they have over running or stotting.
Muley or Whitie, I disagree with the cactus theory....looking at his coat and the "fresh look" to the velvet. Then again, I aint no expert, just my .02 worth.
I saw a show on this buck a while back. It's a whitetail buck at a breeding farm. I think that they said that he is the whitetail ever recorded and he was only about 5 years old.