Grass is hard to digest. That's why cows chew an average of 50 times per minute - a total of 30,000 times per day. Even if we humans really make an effort, we generally don't chew a morsel of food more than 30 times. Cows produce over 150 litres of saliva per day as a result. This makes them very thirsty, so they also drink a lot of water: up to 180 litres per day. This is equivalent to a large bathtub filled to the top. If they are very thirsty, they can even drink 25 litres per minute.