Looks like a hen to me. Brahma?
Corn as a sole source of nutrition is good for neither man nor beast. It is very high in fat, and is unbalanced in terms of other valuable nutrients. It will give you fat birds that are malnourished at the same time. Think of it like chicken candy, a little is okay but too much is not great.
There's no need to try feeding 100% corn. There have been plenty of research articles and clinical trials done that show that 100% - or even much less - corn is not an acceptable diet.