
(thanks fostik)
I feel animals should have at least 5x5 tiles or 8x8 tiles of room to roam or else they will become hostile and start breaking shit and attacking people/other animals. perhaps if your animals bump into one another too often in a big pen they'll become aggressive. (alternatively quality tanks and milk stops generating)
Dwarf fortress has a similar mechanic where if you jam too many animals in too tight a space they'll get grouchy and start attacking each other.
I think this would be cool partly because muh realism and partly because people keep complaining about how animals are currently unmanagable