>It is the brain that concerns me more than any of the other options. What with prions and all that.

I wouldn't trust a brain of an animal that is sold. But for the one you grow yourself, you know what it ate. It's still quite common for people in the suburbs to have a pig or two in a pen in their back yard. They may not be fed the best stuff which would make them grow as fast as they could, but they're still fed right, mostly with kitchen leftovers and dropoffs (potato skins, extra cabbage leaves etc) that still makes this profitable.