Mine grew well, i started off with 4 boars seperated them into 2 pens and named them. Once they birthed more i split them again into another pen and they bred aswell so boars with the same parents will still breed, split them again into another pen and grow your farm like that. kill off any until 2 are left in each pen, you can grow your boar farm exponentially that way. I go off for a couple of days and they still breed when i'm away...