They often get ground up and put back into big animal feeds, which is how animal diseases like mad cow can get passed around, as it did a couple of years ago. It also ends up in dog food, ahich is how they can advertise dog food as being "filled with beefy chunks." The chunks come from a cow alright, but you didn't think you were really feeding Fido sirloin tips did you? I would also be somewhat surprised to find that none of it ends up in human food. Somebody somewhere at the FDA must have decided what is truly dreadful offal, and what is marginally fit for human consumption, and my bet is that the line gets pushed right to its boundary to make an extra penny or two.