GROCALF-Growth promoter for calves The three most essential nutrients for calf growth and development are water, energy and protein. Fibre, minerals and vitamins are also needed, but play a smaller role. The best way to ensure that fed protein is efficiently used by the animals is to supply it in the form of UDP; that is, fed protein escaping rumen fermentation that passes directly to the abomasum for acid digestion. GROCALF is designed with this type of protein.