I am interested in history and living off the land, and when I watched a documentary about ancient toilets, I learned about something called "pig toilets". Essentially, they're a toilet stall built over a pig pen so your excrement drops through a hole inside where the pigs eat it. Remote rural areas in Africa and Asia sometimes have them, and allegedly it makes the meat taste very good.
To be clear, I am not asking because I have plans to do this, but I am morbidly interested regardless. Obviously there are issues concerning whether this is humane or sanitary, but I'm curious whether this would be illegal anywhere whether because of some strange law specifically covering feeding animals feces, or if the FDA might ban meat products from animals having been fed feces.
Is it illegal anywhere in the USA to feed pigs human feces or sell their meat afterwards? Are there any other reasons why a pig toilet might be illegal?