As a pole I approve of this game,
On a real though, the animation on the cows is really nice with a decent variety of different cows, very creative idea, the UI is nice as well.
However, like Others said, I'd be nice to see some sort of upgrade system and Not sure why but for me the cows don't seem to change like in the trailer(Might be a problem with my resolution).
Otherwise, Great idea and pretty funny final outcome, Great Job!