ProDNA is a feed additive containing nucleotides isolated from yeast cells. Nucleotides are the most important component that builds nucleic acids, including DNA. DNA is, in turn, a specific decision-making center of every cell, i.e. in the DNA, all information necessary for the proper functioning of the cell and, to a certain extent, the whole organism, are stored. Despite the fact that nucleotides are found in feed, including colostrum and milk, and the mammalian body can synthesize them on its own, these two possible ‘sources’ of nucleotides may not fully cover the calf’s body needs during intensive growth and development. Hence, these compounds are generally considered to be conditionally exogenous, i.e. conditionally indispensable in the food consumed. The unique feature of ProDNA is that the nucleotides contained in it are first purified and then re-combined in such proportions to best cover the calves’ needs. In more detail, the nucleotides are divided into purines and pyrimidines. Solid feeding stuffs are a particularly rich source of purines, but contain few pyrimidines. In colostrum and milk, the proportions are barely different, i.e. colostrum and milk contain fewer purines than pyrimidines. The addition of ProDNA to the milk replacer makes it possible to balance the amount of purines and pyrimidines taken in forage by the calves, and thus reduces the likelihood of their deficiency during the period of intensive growth.