The level of protective power in pigs depends on the influence of environmental factors and is reflected by the change in hematological indices of the blood, which in turn affect the intensity of metabolic and redox processes. The purpose of the search was to study the influence of feed additive "Butaselmevit-plus" on the morphological indices of the blood and the protein synthesis function of piglets' liver during weaning. The experiments were conducted on the basis of "Koshet" LLC, Mukachevo district, Transcarpathian region. Two groups of pigs were formed -control (C) and experimental (E), in the number of 10 individuals in each group, selected on the basis of analogues -age, breed and body weight. In the suckling period, piglets were kept under sows in special machines, had constant access to the mother, and from 5 days of age -free access to concentrated feed. Feeding of animals was carried out according to the norms for this age of pigs. Clinical and physiological examinations of piglets were conducted prior to the search. They took into account their general condition and activity when eating feed. On the 28 th day of life, piglets were weaned and rearranged from different nests for further retention during the fattening period and growing up with the changing structure of the diet, which served as technological stress for the animal organism. Beginning from 5 days of age, piglets of all groups were fed pre-stern compound feed. The piglets of the experimental group, from 21 to 40 days of age, were additionally fed the compound feed additive "Butaselmevit-plus" at a dose of 100 mg/kg of body weight per day. Weaning of piglets from sows at 28 days of age leads to a decrease in the number of leukocytes by the 30 th day of life with a further increase by the 35 th and 40 th day of life. The use of the feed additive "Butaselmevitplus" contributed to the probable increase of hemoglobin and erythrocytes level in the blood of weaned piglets of the experimental group for the 35 th and 40 th days of the experiment. Feeding of piglets with feed additives "Butaselmevitplus" promotes enhancement of protein synthesis of liver function. Increase in content of the total protein in the serum of piglets blood from the experimental group during the specified periods of the experiment, compared with controls, indicates the stimulating influence of vitamins A, D 3 , E and milk thistle spotted in the content of the feed additive on protein synthesis. Also in the piglets' blood of the control and experimental group after weaning on the 30, 35 and 40 days of the experiment was recorded a higher content of albumin and a lower content of globulins.