It’s challenging to feed water to young dairy calves in the freezing months of winter, but it’s also highly important. And, the earlier calves get access to free water the better!
Milk or milk replacer does not constitute free water, because it bypasses the rumen and reticulum and travels straight to the abomasum via the esophageal groove, which is active in calves until about 12 weeks of age” – Jim Quigley, DVM
Source: Dairy Herd Management, November 2, 2020. Link. Research on water availability to young calves has repeatedly shown that calves receiving access to free water eat more starter grain and gain more weight than those receiving liquids only via milk or milk replacer.