I'd suggest your extension agent, or even the feed store or Co-Op nutritionist.
FWIW, I live in central Nebraska, where there are lots of farmer/feeders, along with irrigation, so any crop planted will grow. I know several feedlot owner/managers personally, and more by reputation, and I can't think of a single one, off the top of my head, that does not use Corn for silage, with the exception of one or two fields on thin soil, on a hill, where corn is much more likely to have a crop failure.
