FYI: Pigs are actually very clean animals, but lack the ability to sweat. They prefer clean and dry usually. In the summer when it is hot is when they need the mud to cool down. If they are white, it also serves as sunblock.
We didn't have a wet area here for our pigs, so I built a shaded piggy dripper to make mud in summer:
https://steemit.com/pigs/@goldenoakfarm/how-to-put-up-a-piggy-dripper
Its always a battle with the dripper. My wife used to raise a pig each year and she went through many iterations of drippers lol. But it was in arizona so I suspect the pigs wanted loads more mud.