Here's what Slanker's says:
"Pastured pigs are fed grain, grain by products, stale bread, and other foreign foods and that makes the resulting meat products only slightly better than conventional store-bought pork. The idea that pigs must be fed grain is preposterous and ignorant.
"Our pigs range at large foraging for their natural food. They graze grass just like cattle. Most of what they eat is grass, forbes, and leaves of trees. But they also eat grubs, roots, acorns, berries, fruits (acorns, berries, and fruits are strickly seasonal), eggs, critters of all kinds, and about anything else they come across in the pastures and woods where they live. (In fact, their diet is about the same as a grass-fed chicken!)"