as much dirt as ours bring in, thankfully, they don't eat until they are gorged, nor do they eat food where they potty.. they actually have a corner of the yard where they go, and won't eat the grass over there...
that being said, farm hogs are disgusting. And to be honest, if you make a pig stay where they potty, they become desensitized to it, and then it stops bothering them, whether they eat where they potty or not. Ours don't, and I'm thankful for that. BUT, I'm not oblivious to the germs they can harbor. Lets just say that I don't eat after the pigs, but I know someone that will give food off their own silverware and won't even wipe it off, unless there's dirt on them, before eating off of it themselves. So disgusting.