If your calf starter has a fiber source (such as oats, barley, etc.) and contains 7 to 11 percent crude fiber, feed only the calf starter grain. Once the calf is eating 4 to 5 lb (2 kg) of calf starter, introduce hay to the diet, but be sure the calf eats the calf starter (source of energy and micronutrients).
To add to Mike's comments, a preweaned calf should get grain only. Once they are eating 2 pounds of grain per day, wean them and get them on more grain- up to 5-6 pounds, then introduce hay.
Mike Hutjens, Extension Dairy Specialist, University of Illinois - Illini DairyNET
Arlyn Heinrichs, Dairy Extension, Penn State University.
