Abstract. The purpose is to characterize the development of the synthetic activity of polychromatophilic erythroblasts and erythrocytes, in particular the status of the hemoglobin-synthesized function of avian erythroid cells in early postembryonic ontogenesis. Methods. The experimental part of the study was carried out in the conditions poultry farm of “Chebarkul’skaya ptitsa” (Chebarkul district of the Chelyabinsk region, Russia). The whole blood of Hubbard ISA F15 broiler chickens of four age groups (n = 40) was studied: group I – 1-day-old chicks; II – 7-day-old chickens; III – 23-day-old broilers; IV – 42-day-old chickens. The scientific novelty. Functional morpho-densitometric parameters of chromatin of the nucleus and cytoplasm of erythroblasts and red blood cells of birds in postembryonic ontogenesis. Cytophysiological and epigenetic parameters of hemoglobin synthesis by erythroblasts and young erythrocytes are important in elucidating the regulation of the functions of blood cells in normal, adaptation and disorders. Criteria for the synthetic activity of erythroblasts and maturing erythrocytes of animals and humans are optical density as an indicator of the concentration of euchromatin and the metabolic dynamics of the cytoplasm, as well as area as an indicator of the distribution of euchromatin in the stroma of the nucleus and the size’s of the cytoplasm. Results. According to the results of calculation of spectral, morphometric and opticometric values of nuclear chromatin, cytoplasm and their indexed ratios for polychromatophilic erythroblasts and erythrocytes, hemoglobin synthesis in early postembryonic ontogenesis is characterized on a model organism of broiler chickens. According to the results of determining the geometric (n = 30) and optical (n = 300) parameters of euchromatin, heterochromatin of the nucleus and cytoplasm, their ratios and indices were calculated for polychromatophilic erythroblasts, polychromatophilic erythrocytes and mature erythrocytes in peripheral blood smears (n = 158) stained by Pappenheim. Cytochemical reactions reflecting the physiological and biochemical interrelations of erythroblasts and erythrocytes are the basis of a complex morpho-densitometric test of the activity level of hemoglobin synthesis by erythroid cells in early postnatal ontogenesis.
