In my dad's time, most farmers bought one spring piglet for fall butchering. One pig can be fine alone -- I guess -- but the only one dad ever discussed was Lester D. Pester and he thought he was a dog.
My cousin tells a story about a trained pig following him around and coming when he called. He said he felt a little bad when he whistled for him and he hopped right into the trailer to take him to market. "But...the bacon sure was good."