Grass is difficult to digest. That is why a cow chews about 50 times a minute, which is more than 30,000 times a day. Even when we humans try really hard, we usually don't chew food more than 30 times. Cows produce 150 liters of saliva per day. This makes them thirsty and they drink almost 180 liters of water a day. That is as much water as there is in a large bathtub that is filled to the top. If cows are really thirsty, they can even drink 25 liters of water per minute.