You can do this early in the game after you defeat the rat in the bar and find yourself wandering around Houton. There are a number of cows in the town. If you walk up to the side of one and interact with it, it'll get tipped over. As you wander around, cows that you tipped will stand back up and you can tip them over again. Once you've reached 30, the achievement will unlock and an enemy cow will appear who will attack you if you get to close.