This is tricky. After completing the game, go to Level 53 and complete the quota (five cows) using the nearby baby cows. Afterward, using the female cow, go around the whole of the level making the other cows follow her. Get them all in a line and you will notice that when you hover near a following cow, it wont move as all it does is what the female does. Because of this you can use your depressor beam on them to make them poo. Get the 3 cows at the back of the line under your beam at once and use slight pressure on the trigger to make them poo a little, too much pressure on them will kill them. Keep doing this until they have made a large pile of poo that isn't growing any further. Do this to all following cows in the line, then move the female forwards to get them onto poo-free ground. Keep repeating and the achievement should pop up after 10 - 15 minutes.