I castrate (neuter) all of my male pigs that are not going to be sold as breeding quality boars to approved farms and homesteads. This can be done when they are very young so males can be neutered before they go to their new homes at weaning of 6 - 8 weeks. It is also included in the price of my male pet pigs.
For females, my vet recommends doing the spay between 4 - 6 months old depending on size and situation. Since most people want to get their new pet as soon as they are weaned and not wait for a 4 month old piglet, I allow the females to go to homes without being spayed first. The additional cost to get a female spayed needs to be taken into consideration. I'm very fortunate and when I got Ripley spayed at 6 months old it only cost me $450. I have seen on facebook pages where people are being charged over $1,000 to spay their pet pig.
Kunekunes normally have their first heat cycle around 8 months old but could go into heat earlier or later. If you do not get them spayed they will go into heat every 19 - 21 days for 1 - 3 days for the rest of their life 15 - 20 years!. Going into heat is very stressful on them because their instincts and hormones take over and drive them to "find a mate".
They can be come aggressive and pushy when they are not getting what they want. One of our girls Clover has actually chased Josh around and was jumping on him out of "frustration". She will chase around the other girl pigs in her pen and when they finally get tired of running she will mount them. Poor Mace and Nugget have learned to deal with Clover when she is being "crazy".
Un-spayed females can also get moody and just do not understand why they feel bad. They may even try to break out of the yard depending on how strong their hormones and instincts are. They can also start to pee in the house or places they don't normally pee to "attract a mate".
Female pigs who are not spayed are extremely likely to develop uterine tumors at some point in their lives. These tumors are often fatal because by the time they are noticed they have swollen bigger than their abdomen.
Please work with your veterinarian to establish when the right time to get your new pig
spayed. My veterinarian kept Ripley over night after her spay because pigs do not do very well with sedation. I opted to have pain medicine for Ripley when she got home and it ended up making her very sick. She wouldn't eat and was throwing up. I ended up taking her back to the vet and they gave her some medicine to calm her tummy and she had to stop the pain meds. She didn't seem to be in much pain and her stitches dissolved in 10 days.