Unless you plan on breeding your pet pig, s/he should be spayed or neutered. Males are neutered and females are spayed.
Male pigs are usually smelly and very aggressive if not neutered. Neutering helps avoid infections and cancer of the reproductive organs. Male pot-bellied pigs can become sexually active at 4 weeks old and can be neutered by 5 weeks old. Other pigs are neutered before 6-8 weeks old.
Female pigs can be spayed at 4-5 months old. Performing spay at this age is safer as there is less fat in the abdominal area making surgery easier. The majority of unspayed female pigs eventually develop cancer, halving their life expectancy. Even if you have a female pig with no males close by, spaying can increase her lifespan.
Both sexes make better pets after being fixed. They have calmer personalities and are much more pleasant to be with.
For a happier, healthier life, spay/neuter your pet pig to avoid unwanted behaviors and to help prevent disease.