Why don't deer get sick from eating corn in corn fields?
Why does anyone think they don't?
Deer can actually get quite sick & weak from consuming aflatoxin corn, but few people seem to be aware of this. One thing not mentioned is how in their weakened state, they are more vulnerable to predation, so we come back to blaming the coyotes. But sometimes, it's the weakened deer that came first, coyote took advantage.
That said, I don't believe aflatoxin develops as much when corn kernel's are still impregnated into the cobs. Also, widely scattered loose kernels, such as is left in a large corn field, don't seem to develop aflatoxin as readily as kernels that touch each other. I also suspect the wind keeps many harvested corn fields in a dryer (less humid) state than the depressed muddy areas around most corn feeders.
Many people believe big ag areas with lots of corn fields grow bigger deer because of those corn fields. I will argue it has as much to do with the soil and other high quality forage as the corn. It's just that such areas are also often good places to grow corn. In fact, increased corn consumption in the summer time (from feeders) can actually reduce the antler sizes when the deer consume less protein-rich plants because the deer are eating more high sugar (carbs) corn which is very low in protein.
Highly soluble protein, as found in clovers, soybeans, and ragweed helps bucks grow larger antlers. The presence of summer fed corn reduces those bucks' consumption of the high protein foods. Kinda like giving candy to a toddler for breakfast instead of something more healthy.