use good walls, not the 'fence'
fence is easily broken by the untamed animals and mobs

on my good pen i use the low brick walls (and doors), easy to jump over (and throw food over) and stops small mob attacks

build a workbench in the middle to stop enemies from spawning in it

on my main building i put the boars in my moat around the house, just keep throwing food (and overstock bones and greydwarf eyes) down to them