After birth, the calves are lovingly licked dry by their mothers in their stall. After just a few days, they can join the other cows out on the pasture to frolic around and play. A few weeks later, they start eating grass and hay. However, they still cant digest the fresh green fodder as well as adult cows. Thats why calves keep drinking their mothers milk for six to twelve months. They are fully grown by the age of around five, and can live to an age of between 20 and 25.