I researched a little bit re Missouri and USDA. Like others said, there are exemptions for small operators that process less than 10,000 or 20,000 or whatever. What I noticed though is that they like to maintain a grip on it and insist that your processing is done to certain standards. Bottom line is that they are kowtowing to the large processors like Tyson and such. I just sell mine by word-of-mouth advertising. I go to great pains to ensure I process clean animals and no doubt they are better than store bought because they haven't endured the conditions factory chickens have and they get no antibiotics or hormones or animal-based feed. I would think that unless you threatened the local Tyson factory, you're probably safe selling your own on a small scale.