Baby calves need water. Research by Donna Amaral-Phillips, University of Kentucky, shows that, starting at four days of age, baby calves should be fed free-choice water along with their calf starter, as this will increase starter intake and weight gain. In a research study, depriving calves of drinking water decreased starter intake by 31 percent and decreased weight gain by 38 percent over those calves provided water free-choice.
Amaral-Phillips explains that free-choice water, along with a high-quality calf starter, helps develop the rumen so that the calf can digest forages. When calves are fed milk, she said the milk does not enter the rumen but rather the calf’s true stomach or abomasum. Thus, milk or water added to the milk will not provide a moist environment for the bacteria to grow in the rumen.
Source: Professional Dairy Producers of Wisconsin