Grain
Kunekunes can fatten on pasture grazing alone. If you do supplement with grain make sure it is 16% or lower in protein. I used the feed store's brand "Bryant" 14% Hog Finisher twice a day. I have recently switched to Purina's Pig & Sow from Tractor Supply. It is a 16% feed and I've noticed it helps reduce the tear discharge from their eyes. Depending on the size of the pig and how much pasture they are getting I adjust the amount.
Feeding Growing Piglets
Piglets start eating grain as early as 1 week old, they follow their mom out and will mouth the grain. By 3 to 4 weeks old they are fighting their mom for food. When they are weaned at 8 weeks they are getting 1/2 cup twice a day and fresh fruit and veggies. These are rough estimates for growing piglets. All piglets will grow at different rates and food needs to be adjusted accordingly.
2 months - 4 months ~ 1/2 cup twice a day
4 months - 6 months ~ 3/4 cup twice a day
6 months - 8 months ~ 1 cup twice a day
8 months - 1 year ~ 1 1/2 cup twice a day
1 year - 1.5 years ~ 1 3/4 cup twice a day
1.5 - 2 years and older ~ 2 cups twice a day
I supplement with hay in their pens when they are not out grazing. They also get fresh fruit and veggies. For reference Mazuri mini pig feed has a feeding chart.
The most important thing is monitoring your pig and adjusting as needed. It's a good idea to take pictures once a month and compare the pictures to see if they are gaining weight or getting skinner. It's hard for you to tell just by looking at your pig since you see them every day. If you have monthly "check in" photos it will be easier to evaluate their body condition. I find it easiest to look at my pig's butts. You don't want a big saggy butt, if you see that, that are overweight. You just want a cute little piggy butt. #3 in the AMPA chart below is your ideal piggy butt. Also pay attention to your kunekune's face, they should not have huge overhanging jowls and you should be able to see their eyes. Fat blindness is something that can easily happen if their face gets too fat, the fat rolls will block their eyes and they cannot see.
Fat Blindness
If your pig is getting fat blindness, make sure you are feeding a quality feed. Do not feed kunekune's "All Stock" or any type of feed that is for other animals. Our veterinarian said the #1 reason she see's health issues in livestock is from "All Stock" feed. Then if you are feeding a good quality grain, cut back on treats and fruit. Still feed veggies and they can get hay and graze. If you are still having issues, take your pig to a veterinarian to make sure nothing else is going on.
Water
Pigs do not have the ability to sweat, so it is very important to provide them with a pool or mud wallow. The mud in the summer will prevent them from getting sunburned. Clean drinking water is very important as well. We have to wash out and fill their waters daily. For piglets a cement mixing tray works well. We also train all of our pigs to drink out of nipple barrel waterers. You'll need also check that the nipples are flowing correctly daily, they can get clogged or broken. Pigs are very susceptible to something called Salt Toxicity. As a pig owner is is very important to know about salt toxicity its an imbalance of salt in your pigs system and it can happen just from being deprived of water for a few hours. It's almost always fatal and it is extremely difficult to treat. It's easily preventable by making sure your pig always has access to fresh water. They should have multiple water sources and it should be easy to access. Ripley is very picky about her water and will stand at her bowl waiting for me to clean and refill it. She will not drink out of a dirty water bowl.
Supplements
Food Grade Diatomaceous Earth - 2% of feed, So add 1 pound to a 50 pound bag of food. Helps as a natural dewormer.
Black Oil Sunflower seeds - Natural Dewormer for chickens and helps the pigs maintain a healthy coat.
Coconut Oil - I freeze ice cube trays with coconut oil and feed as a treat. Helps with a healthy coat and with dry skin.