I used to coyote hunt on a cattle farm that was literally covered up with them. One winter an old bull died, and I figured I'd kill a pile of coyotes hunting over the carcass. Nothing touched it.............not buzzards, nor possums, nor coyotes. It just lay there and dried up to a pile of skin and bones. You could see where the coyotes did drag off a few bones eventually, but I thought maybe the hide was so tough that nothing to tear their way through it in order to get to the meat.
I've seen the same thing on several other cattle farms I've hunted, including my own. They just don't seem to go after the older animals like they do a smaller one. There are several deer hit my cars every year out on the highway next to my driveway, as it's a major deer crossing there. I'll always drag the deer off the road, and put them in a back field with the idea to hunt over them. I've found that they don't last over a couple of days, until there's nothing left. I guess venison tastes better than beef.
My curiosity is killing me... to test your theory did you ever try to go over and cut the dead cow open so there was access to at least the internal organs? It seems those are the first things they take on deer and elk... once accessed, they might hang around for a free meal...
