Enemy cows become giant from eating too many hamburgers made of hatred and contracting mad cow disease (3 small burgers to go from normal size to mid size and 5 more to go from mid size to large, and the large burgers created when you kill an enemy instantly upgrade them to large). It doesn't quite work as well as I intended it to since it was the last thing to be implemented and I was getting tired so I didn't try to polish the mechanics.

It just kills the traitor cow instead of making her hulk out through the power of hatred (because the cows are seething with hatred towards the traitor trying to kill them and thus want revenge at any cost). Taking hits from the small burgers does slightly increase the damage of the hatred beam but it's not advisable since five small burgers is enough to kill you.

An extra bonus tip in case no one's noticed it: there's special "pacifist" rankings in the game if you're able to obtain a high score without directly killing enemies which is possible by luring them into the slaughterhouse (since it gives you bonus points but doesn't actually count as a kill)