Most of the pigs raised today are bred to be relatively hairless because nowadays it's a waste product. Most just have a thin coat of bristles which nevertheless can be used for fly tying especially if they are dyed. Mammals are generally two coated with outer guard hairs and an inner coat. The inner is usually shed in the spring and regrows in the fall. In the past hairy pigs were valuable because the inner coat helped them keep warm. Obviously this trait is no longer useful and has been bred out of modern hogs. There are still some rare breeds of hogs that are closer to the original wild hog and retain an inner coat of hair. Such hogs have been disappearing from the American farm scene since the 1950's if not earlier. Bill