In order to prevent and maintain the normoflora in the gastrointestinal tract of poultry in the composition of compound feed include various biologically active additives that reduce the pressure of environmental factors on the body. Such additives include a wide range of pre- and probiotics, vitamins, mineral complexes. The purpose of the research was to compare the effectiveness of the use of probiotic feed additives in the diet of replacement young poultry of meat productivity. The tasks of the research were to analyze the dynamics of growth of livestock, its livability, homogeneity of the group, the development of genitals and expenditures of feed for the rearing of replacement chickens and cockerels. The use of the probiotics Levisel SB Plus and Cellobacterin-T in the diet of replacement young poultry at a dose of 0,50 kg/t of compound feed in the period from 3 to 45 days allowed to time of transfer of chickens in parent stock to increase the absolute live weight gain by 4,4 and 2,0 %, to increase the livability of livestock by 0,6 and 0,4 %, yeild of pullet crop by 1,1 and 1,9 %, respectively, Live weight of cockerels that have received probiotic Levisel SB Plus at the age of 147 days exceeded the control group by 2,2 %, and in group has been receiving probiotic Cellobacterin-T it was lower by 1,1 %. At the same time, the livability of the livestock in the groups have been receiving probiotic was higher by 5,1 %, the homogeneity of the group by 0,6–1,9 %. The use of probiotics contributed to an increase in poultry excrements of lacto- and bifidobacteria, a decrease in the group of enterococci and conditionally pathogenic. Probiotics have stimulated in chickens development of organs of ovogenesis, in cockerels of testess. The use of probiotic Levisel SB Plus in the initial period of postnatal development in poultry helped to reduce the expenditures of feed on the rearing of chickens by 1,0 %, cockerels by 1,3 %, and the probiotic Cellobacterin-T, respectively, 7,4 and 10,6 %.

Normalization of the bacterial background of the gastrointestinal tract and the reaction of the environment largely contributes to the growth and development of poultry in accordance with the standard of cross. The addition of the prebiotic Salmocil F to the diet of replacement young poultry at the dose of 0,6 kg, 0,8 and 1,0 kg/t of compound feed allowed the poultry to grow to 18 weeks of age with a live weight of 1836,2 kg, 1915,4 and 1885,0 kg, respectively, which was higher than the control group by 0,7 %, 5,0 and 3,3 %, and the uniformity of the group by 8,0–9,0 %. The prebiotic Salmocil F contributed to the better development of the replacement young poultry such as muscularization of the pectoral muscle, its tone and physical shape. The prebiotic Salmocil F excluded the reason for the culling of poultry in the experimental group for toxicosis and intestinal intussusception, increasing the livability of livestock in the experimental group with the low dosage by 3,0 %, with medium and high by 4,0 %. The low dose of prebiotic in the diet of poultry of the 2nd experimental group in comparison with the 1st control group reduced expenditures of feed by 5,5 %, the average rate of input in the 3rd experimental group by 6,7 %, the high dose in the diet of chicks of the 4th experimental group by 6,1 %. The feed-conversion efficiency for receiving replacement young poultry per each 100 kg of feed fed in the group with the dosage of 0,6 kg in comparison with the control group was higher by 6,0 %, with the increase to 0,8 kg by 7,2 and with the addition of 1,0 kg/t of feed by 4,1 %, and in value terms by 5,4 %, 6,5 and 5,6 %, respectively. More optimal is the dosage of 0,8 kg of the prebiotic Salmocil F per 1 ton of compound feed.