Here is something I never thought about until yesterday when I was talking to my Dealer that is a large dairy farmer.  Feed corn to deer, especially year round, is a bad thing.  They are ruminantes like a cow. If you feed a cow to much grain (or to long) their feet will get sore and grow impromperly aka founder. Which makes them lazy and unable to walk far. Cows also get fatty livers and when they give birth get acidosis and milk fever which are deadly. 

He summized that this is why the deer population in northern Wis is so low.  People feed a tremendous amout of corn to deer, many year round.  If this effects them like a cow, this is could be an answer.  He said the best thing to feed deer is mineral/salt mixture.  He has deer around his cattle mineral feeders all the time.  To grow big racks, you need mineral (calcium/phosphorus, etc) and forage, not corn.