Pot Bellied Pigs/Birth defect
I am a Pennsylvania based breeder of Mini-Potbelly pigs. On valentines day one of my females had a litter of 5. One of the boys has a curled up front leg. It seems like the ankle joint is backwards. It doesn't seem to be causing him any pain, but I am just not sure that a pig can live with only three supporting legs. Obviously he can't be sold or bred, but he is eating and seems healthy. In your experience have you ever heard of a pig with three legs?
I have heard of pigs adapting to life with three legs. But, it isn't always easy for them. Pig bodies are stiffer than dogs or cats, so it's harder for them to limp on 3 legs. Pigs are prone to obesity and arthritis, both are trouble for a lame pig.
Assuming there are no other birth defects, he stays at a healthy weight, does not develop severe arthritis and his environment is adjusted for his handicap, he should have a good life. Old age may bring unforeseen or unpreventable problems, but for now that is a long way off.
Arthritis may not be completely preventable but there are steps you can take to reduce the stress on his joints. Never, ever ask him to walk on any slippery surface, like tile, ice, etc. Get some cheap carpet runners (they can be ugly!) and stash them near potentially slippery surfaces.
Avoid difficult walking surfaces, like deep soft sand. Limit his time on asphalt or concrete to just a few minutes, do not let him stay in a concrete pen. If the floor of his shed is concrete, get a padded mat designed for horse stalls. Do not let him attempt stairs, provide a gently sloping ramp.
I would not tamper with his diet until he's naturally weaned. At that point, I would add extra dairy to his food. I would think about starting him on a joint supplement right away, long before any problems have a chance to start.
His feet will need some special attention. I'm sure the problem foot will not be able to wear down the hoof naturally. His other three feet will need to be kept short, even a slightly longer hoof will make it harder for him to move around.
Of course he will need to be neutered, so the vet can give him a very complete physical at that time. I'm sure he will be a wonderful pet.