I don't think I would try and shoot a deer off a bow at all... I would try and shoot an arrow.
I kid, I kid.
Anyway... most of the answer to this is going to depend on your draw length. 50# at 29" will throw an arrow with plenty enough velocity to kill a deer out to 35-40 yards. If your DL is only 22" (like my wife), then you are looking at 25 yards or so, and that's with a sharp broadhead on a good heavy arrow.