I don't have specific information on this, but I've long felt the best kind of "wildlife feed" is planting things they evolved eating. Anything else not only can cause dietary problems, but I also feel the concentration of animals in a small area is a risk for the spread of disease. In almost all cases I feel new plantings (or replacing useless plantings) are a better investment than buying feed for wild animals.

Midwesternerr, I agree with you. At my house, I plant native trees, shrubs and flowers that feed wildlife, and I only supplement with a birdseed mix or critter mix when there's a particularly bad winter's day, like an ice storm.
But my dad insists on feeding his deer, so I would rather he at least feed them something that doesn't actively harm them!

I like your phrase "replacing useless plantings" -- there are so many useless non-native ornamental plants out there! And it seems every house in my neighborhood has them -- lined up in neat geometrical patterns! Around here it's bradford pears at each corner of the house, leyland cypresses along the property lines and crepe myrtles lining the driveway... oh, and also the mandatory straw bale, pumpkin and potted mum by the doorstep in fall, and cloned pansies around the mailbox in winter.
(Sorry for going off-topic; it's past my bedtime.)

Taragirl, I agree with you totally that selecting and planting vegetation compatible with and edible by wildlife makes the most sense. It also encourages "native" plant gardening. Whenever I research new shrubs to add to my garden, I try to select ones that have berries or seeds that are preferred by birds instead of hybridized clones that look pretty only.

While I can't say anything about the peanuts, I have to question the corn findings. As a farmer who has first hand experience with this, corn is one plant that is attractive to many different animals from the time it sprouts to the time the cobs are lying in the field picked clean of the last kernel in winter. Of course corn in these diets is supplemented with other natural foods, but it is a main item, especially for deer. Part of our ongoing problem here in the Midwest with deer overpopulation is due to the fact that row crops, especially corn, provide both easy forage and cover. Imagine lying in bed, getting a hunger pang and just stretching out your neck to pluck an ear of corn. And if the ears are not on yet, then the fresh shoots at the tip of the plant will do ok , too. A healthy doe can produce twins and triplets if conditions are right, and if you combine easy energy sources and high birth rates with a virtual lack of natural predators, a population increase is inevitable. There have been numerous meetings locally between the DNR and concerned farmers over the impacts that deer, turkeys, and other animals are having on crops when numbers get too high for an area. Some want to blame the DNR, some want to blame hunters, the hunters want to blame the activists for giving hunting a bad image, and it's really just simply another example of the ripple effect caused by human activities on the planet. Personally, I am much more concerned with the effects too many deer have on OTHER ecosystem than what they do to an 80 acre monoculture field of corn or soybeans.

Perhaps the study is dealing with diets of animals that are primarily corn based and not naturally supplemented? If anything, consumption of corn seems to be driving numbers up, not down.
Just as a parallel thought:
During the severe drought of 2007, I noticed a drastic increase in the number of road killed squirrels here, and I assume that these animals had abandoned the woods where the mast crop had been a near total failure and were travelling over hazardous open country just to reach a corn field for food.