This article describes the effect of pre – and probiotics on the intestinal microflora of newborn calves.   It is proved that one of the most effective ways to restore the imbalance between the ratios of the main groups of intestinal microorganisms is to protect the normal microflora by feeding animals with pre – and probiotic drugs instead of traditional antibiotics.   The lack of scientific requirements for the use of prebiotics, in particular lactulose, in the practice of raising young farm animals for the prevention of gastrointestinal diseases makes it difficult to promote them on the veterinary market.   Most probiotics do not show their useful properties due to the fact that the strains in them are not able to actively spread to the intestinal wall. In this regard, in recent decades, there has been an interest in finding ways to normalize the intestinal microflora using prebiotics.   It was found that in addition to lacto - and bifidobacteria, the intestines of calves contain opportunistic bacteria, such as E. coli, staphylococci and streptococci. When taking pre - and probiotics in experimental groups of animals, there was a decrease in the content of opportunistic microflora with a dynamic increase in obligate, which indicates a positive effect on the formation of intestinal microbiocenosis in the milk period. Moreover, more noticeable changes were found in the study of faeces of calves of the second and third experimental groups, which were fed probiotic "Vitafort" in its pure form, and especially a mixture of Vetelact and Vitafort.