You can feed them sugar beet to help fill them up, and its cheaper than nuts... don't feed purely sugar beet though as they wont get everything they need. Someone I know just feeds their pigs barley and soaked sugar beet, and any fruit/ veg from the garden, and the pigs get the rest from the ground (personally i'd do a soil sample if expecting to get everything (extra protein, minerals, vitamins other amino acids) from the ground, but thats just me) pigs seem ok.