I knew someone who had some land and raised a few pigs. He slaughtered them himself for pig roasts but always used a high powered firearm. One shot to the head with a 12gauge deer slug at close range did the job quick and mercifully.
My grandfather raised a pig every year.
It would follow him around like a puppy all the time until it was it was time to go into the smoke house.
I prefer the Walmart meat aisle.