NSFL: TIL about "Four D meat"

A friend was talking to a young butcher telling him about how this crazy guy comes to the supermarket to BUY rotten meat! Butcher kid can't think of WTF anybody would to do with rotten meat. My friend tells him it's probably to make dog food.

Later my friend find a post that talks about Four D meat: Dead, Dying, Diseased, or Down And how it is used to make dog food

The link above point to a dog search on the topic