You don't see that every day

Coming home from work today, going South on I-69 around mile marker 109 or so, I came up behind a bad-smelling dump truck. The closer I got to it, the worse it smelled. Finally I moved over to the passing lane and saw that it was a dump truck full of full-grown, dead cows... there must have been 10 or 15 in there for them to pile up that high. That's a large investment to have lost for someone, and for the beef to have gone bad (by the smell) already... what must have happened?