@ that age, you should let him eat as much as he wants. If he has a really good appetite & eats everything you put down, divide his meals into 3 or 4, space them out throughout the day so he doesn't go hungry. The amount of how much to feed should be on the bag.
One thing I learned bc I have a widdle piggie
if he eats too much, his poopie will be on the soft side...but he's always hungry & will eat until he throws up.