I love the game as well when it comes to the animals, but for the horses, this is what Hayo said about it:
I don't know xD There's always something else to do and those stallions are just being pushed away every time. But I'll put them... eventually.
Since the next update on his twitter/pateron seem to have the rats mention based on the picture of the wererat, he might be adding those next as well as anything else he can put into for the next version when it is released on Itch.io for the public.