At present, you can configure the animal farm for maximum number of pigs, sheep, cows, and chickens. While at the time it likely was last looked at there wouldn't have been much value in butchering horses, it's not unheard of with a number of mods for horses to have some specific drops, and nowadays we also have rabbits and llamas.

These should probably be supported in the animal farm, ideally with per-animal settings on whether to butcher excess or simply stop breeding the specific animal type when its limit is reached.