like mchusker mentions spoilage can significant. but in most cases it's only a small percentage. most times the driest grain is put in the pile, so any moisture on the grain rewets it and counteracts spoilage shrink.   a lot depends on how the piles are made, obviously, impromptu piles suffer the most.   and like mchusker mentioned there are companies that specialize in damage grain brokering, with most of the damaged grain going to cattle feeders.  when e-plants  where initially fired up here it was thought that they could utilize damaged grain, it has since been found out that was a bad idea.