Description: The aim of the present paper is to review the differences in chemical composition between colostrum and milk in cows. The concentrations of many nutrients (proteins, vitamins, minerals etc.) and biologically active substances (immunoglobulins, enzymes, hormones, growth factors etc.) are many times higher in colostrum than in milk. A special attention is given to insulin-like growth factors (IGF-1 and IGF-2) - the predominant growth factors in the colostrum of cows (especially in the first portions) unlike many other species and men. Furthermore, IGF-1 and IGF-2 are the most important factors stimulating tissue and body growth and development in newborn calves