Biggest concern is for other wildlife, quail especially, that is exposed to corn used for feeding deer that is contaminated with aflatoxin. Random samples have shown fairly high levels of this contaminated corn used in automated deer feeders in Texas and other Southern states. Not as much of worry in Southern states but supplemental winter feeding with corn in the north can cause problems (acidosis) if deer are not gradually acclimated to the corn in small quantities, due to the lack of an enzyme that's required to break down the starch in corn not being present in a deer's rumen during the winter months.
In both cases, if you are going to supplementally feed deer, pelletized protein feed is a better way to go, although it's consideraby more expensive. The other alternative to supplementally feed is to plant food plots.
Concerned Sportsmen of Michigan