There is a type of stock beet called a Mangel (spelling) more like a sugar beet. I don't think potatoes would work as they are a member of the nightshade family and are probably toxic with stems and leaves. The stock beets may work in the north where they grow better. Peanuts are best in the FL Panhandles sandy ground. They probably being a legume have the best complete proteins that pigs can use. Now the drawback is I would consider pork run on pasture rooting peanuts unclean unless properly wormed. Tape Worms. Swift and Company at one time long ago only used pigs that had been fed on cement floors that had running water over them available to keep them clean and keep the tape worms out of the pork they sold.I didn't find it so. But I love scones and they are def worth it!... can't eat them so much now, gotta watch that blood sugar.
(Feeding pigs by letting them harvest peanuts themselves) not to mention easy! Could you do the same with, say, potatoes or sugar beets? Or do only peanuts provide the proper protein?