This year's Midwest drought will have some effect on grain supplies. How much is yet to be seen. My brother farms about 800 acres of corn and I asked him about this last week. He said he's expecting a 5 to 10 percent loss. The good, fertile ground will still produce good crops but the slopes and sand pockets aren't going to produce nearly as well. Keep in mind that it's been really weird. The rains have been very spotty - some farms have gotten million dollar rains at the right time, but a farm 3 miles away might have only gotten a quarter inch from the same storm.
The Dakotas and some parts of Minnesota are worse off than we are. Much of Nebraska seems to be doing better than us, as is Missouri. I doubt that the actual supply of feed corn will be so short as to be unobtainable, but people are going to pay more for it...