The purpose of research was studying the effi- ciency of application of probiotic "Olin" and prebi- otic "Vetelact" when growing calves colostrum and milk periods. The objectives of the study were to establish the impact of these drugs on the growth of animals, to determine economic efficiency of pro- and prebiotic in the production conditions of LLC "Maslovo" (Oryol Region). The object of the study was young growth of colostrum and milky periods of black-and-white breed. For carrying out the ex- periment three groups of calves having 6 heads in each period of growing on the principle of analogs were formed. In accordance with the dosages rec- ommended by manufacturers, the calves of 1-st experimental group received probiotic "Olin", 2-nd - prebiotic "Vetelact". Mechanical lever scales were used to determine the weight of animals. The re- sults of calves growing of colostrum and milk peri- ods showed that at the end of the experiment theweight of animals of 1-st and 2-nd groups sur- passed control by 3.7 % (P<0.05), 4.4 % (P<0.05) and 2.6 % (P<0.05), 4.5 % (P<0.01) respectively. The average daily and absolute growth of colos- trum and milk calves in group 1 and 2 was respec- tively higher than in control by 16 %, 23 % and 12%, 21.6 %. Based on the analysis of the cost of feeding and the resulting absolute weight gain of calves, possible economic result from the use of studied additives was calculated. Thus, profitability index from calves of colostrum and milk periods in groups 1 and 2 was higher than in control by 4.1 %,1.8 % and 8.7 % and 6.3 %, respectively. Accord- ing to the data obtained, it was concluded that the use of drugs had positive impact on the growth of calves of both age groups. In addition, feeding prebiotic "Vetelact" (group 2) demonstrated the best results in the increase in final live weight and daily weight gain of the animals, however, the eco- nomic analysis showed that at the enterprise it was advisable to use probiotic "Olin" (group 1).