What is that smell?

I get in my pickup this afternoon and smell something kind of rotten. I had not been in it since Friday morning. As I run my errands, I leave the windows down in hopes that it will air out. When I get back home, I decide to find out exactly where that rotten odor is coming from. I am thinking that the guys at work have found a dead fish in the river and decided to play a prank on me by putting it under my seat, they do this sort of thing all the time. Then I remember that on Friday I had gone down to pick up a dead pig (Little Dipper). Further investigation reveals that a pack of sausage had fallen into a compartment next to the back seat. The package had burst open, what a mess!