Creep limitations and critter issues

I have found a very annoying limitation to unit creation. You can only have like 4 custom creeps! The other ones show up, but if you try to place em you get a kid, sheep, rat or another stupid critter. It's true that i have like 20 custom units in my map (DK), but i still don't see why anyone'd put a limitation on this. And another thing, Blizzard put rats, pigs, dogs, sheep and various other critters in the game, but where are the chicken and the cow?! I would much rather want a chicken than a rat, like he could do some wandering near Human Chicken Farms or something and i think a cow would be insanely cool too, especially if you make him a custom unit that explodes on death! But maybe some peeps will make these with the new model editor, i sure hope so. Anyway, if you have any ideas on one of these topics, post a reply plz.

hmm that is because that happens when the list of units in the layer itself becomes too big. Problem to solve is either to switch neutral hostile etc