Pigs believe it or not are contrary to their reputation are actually a clean creature even if does lay around in the mud. His tusk were to long to, they needed to be docked.
I want to add to that, I'm no farmer, but I've been told the main reason pigs lay in mud to begin with is to keep cool, as they don't have sweat glands.
Correct and it keeps the bugs off of them, if you ever go out in the swamps or woods, try putting mud on instead of bug repellent and see which side gets bit the most. Skitter's can't bite through mud.