Commoners must be an awfully forgetful lot, because I am going to assume that if they are a farmer, then one of their parents was farmer, then one of their parents before that and so on. Why do I say this? Well, parents usually teach their children about the world, which for a farm probably includes the livestock they are raising, the crops they are growing, and some tales to keep the little ones entertained at night. Again, the point? Well, knowledge checks are what you remember/recall, so going by the interpretation of Cyclone Joker the commoners would not remember a single detail about anything they attempt to identify, even if they had been told a million times over the past twenty years, they would remember nothing. Yes we all know he won't budge on this, so the point? Okay, okay I am getting to it.
Where in the rules does it state that you HAVE to role a knowledge check to attempt to identify something you meet? In most cases that seems to actually make you forget what you know about a certain animal, so don't try to identify something, work with what you can know without knowledge.
We can't identify a cow (or whichever such animal we wish to use), but we do know that our father claimed the thing in that pen was a 'cow', and that every day since he taught you, you have come out and gotten milk from it. You need to buy another of these 'cows'? All that must be done is a comparison to figure out what you are buying is or is not be what you are looking for.
We can't identify a skeleton (creature), but we can know what a skeleton (bone structure) is and that it can't normally walk by itself, though we don't know what creatures have skeletons or what each creature's skeleton looks like.
So the question for Cyclone Joker:
What happens, according to the rules, when the guy next to you (who has ranks in knowledge) says something is a cow (more details may or may not be given) and then you attempt to identify it (without ranks in knowledge)? Do you forget what that person just said six seconds ago?