One of the approaches to the creation of biologically active additives in pig nutrition can be the use of phytopreparations, in particular, 20-hydroxyecdysone (20-GE), which regulates protein metabolism in piglets. The aim of this work is to assess the effect of 20-GE on the metabolism of proteins in the body and to measure their turnover in growing boars. The experiment was carried out on boars (б Danish Yorkshire * $ Danish Landrace) from 60 to 120 days of age. At the age of 60 days, boars were divided into 2 groups: control and experimental, fed with feed with a content (g / kg) of crude protein 158.7, lysine 7.7, threonine 4.8, methionine 4.6, exchange energy (EE) 12.7 MJ / kg. The ratio of the first limiting amino acid lysine to EE was 61%. The boars of the experimental group were injected with 20-GE at a dose of 1.6 mg / kg of body weight. In boars of the experimental group, compared with the control, there was a decrease in urinary nitrogen excretion (by 26.8%, P<0.05). Nitrogen retention was higher in boars of the experimental group by 19.0% (P<0.001) compared to the control. The results of studies on protein turnover obtained using a stable isotope indicate that the anabolic effect of 20-GE is determined by an increase in the rate of protein synthesis at the same rates of their degradation, nitrogen flow against the background of a decrease in its endogenous losses. 20-GE by activating a signal through protein kinase B provides an increase in biosynthetic processes at the stage of translation. It was concluded that the use of 20-GE in boars cultivation increases the efficiency of using amino acids for the synthesis and deposition of proteins in the body.