I was going to suggest new animals to be added to the game, but after messing with the save files I found that it was already part of the plan. Here is photo evidence.
So I might have just ruined the surprise of some later pre-pre-pre-release, but at the moment they aren't very interesting. Chicken apparently lay eggs, but the item is buggy and turns invisible when you pick it up. Otherwise, right now they act just like cows. And their models obviously aren't complete. This leads me to believe that they will be improved and actually added to the game or deleted from the game and forgotten forever.