Do pigs respawn in minecraft?

I think you have to save a few to let them breed.

Animals do not respawn if you kill them in their natural spawn area. You would have to keep at least two of them alive and breed them to repopulate the species for further farming purposes.

Pigs are no exception, though breeding them requires carrots, which have a chance of spawning naturally in NPC village farms, or may be dropped randomly and rarely when killing zombies.