Mystic Valley Dairy in Sauk City, Wis., uses a plate cooler to warm milk prior to feeding its calves. The dairy pasteurizes about two to three days’ worth of milk and stores it cold. Then, a plate cooler with circulating hot water is used to warm the milk prior to feeding. “To control the temperature, we use a restrictor on the milk side,” says Mitch Breunig, dairy owner.