OK, I assume you aren't being strict when you say "strictly" and that you are including a supplement because 100% corn is not a healthy diet. There is a disease in humans called Pellagra (a deficiency of B3) that no one in the US gets anymore because so many foods are vitamin fortified these days. Pellagra causes diarrhea, mild to severe dementia, and eventually death. In the early 1900s when they were trying to figure out what caused pellagra, experiments on prisoners of an all corn diet (corn bread, whole corn, and other corn products) resulted in the prisoners going mad to various degrees after weeks on the diet. Many of them begged to be let off the diet. I've never read anything about pellagra in swine, but I'll bet pigs would have the same problem.
And then there is the problem of adequate protein. Haypoint just posted in the swine feed thread that a good diet consists of:
2/3 ground corn, 1/3 ground soybean, add a mineral mix designed for pigs, free choice. A flake (2 pounds) hay per hog per day, substitute a bucket of garden weeds when available. A 5 gallon bucket of fruit per hog.
That's good advice and there are a thousand ways you can substitute other things for soy to add protein (Highlands uses whey) or substitute for corn to add calories (potatoes, sweet potatoes, beets, turnips, etc), but you should not substitute corn for soy and vice versa.
Reed the feed sticky and you'll find lots of other alternative feeds if you are interested in that sort of thing.