Road Kill

OK, so I have always wondered who cleans up the animals that have been tragically annihilated by oncoming traffic. Yesterday I finally saw a truck cleaning up a deer left on the side of a road. Just in case you were wondering as well, the DOT has a flatbed truck they use to toss the animals into. But instead of answering a question, it instead leaves my perplexed. What do they do with the remains? Do they just toss it somewhere and let it rot? Does it just go to our landfill (I wouldn't want to end up there)? Or do they clean it out and use it for something? In fact I'm not all that certain I want to know, come to think of it...