As I understand it, feeding corn in winter can be detrimental only if too much is introduced where corn is not in their diet now. I did a resaerch paper on this back in college few (30 or so) years ago and it's only dangerous when deer are fed large quantities of corn when they are starving or close to it and it hasn't been part of their diet up to that point. It's more likely to be of no benefit than a danger and it's only when a large quantityis dumped in say a large tract of hardwoodsduring a bad winter with no agriculture in the area and when the deer are already stressed is it dangerous.