The article presents theoretical and experimental substantiation of relationship between the content of trace elements in the soil, water, feed and blood of mare with hypocobaltosis and hypocuprosis in biogeochemical province of Transcarpathia. The total content of Zn in soils is 50.96 mg/kg, Cu – 16.32, Co – 7.14, and Mn – 493.97 mg/kg. It was established decrease in the concentration of mobile forms of Cu and Co (0.01mg /kg), Cr (1.93), Pb (1.66), Ni (0.67), Zn (1.42). Also, in water from artesian wells of research farm it was established decreased content of Co (by 3.3 times), Cu (111), Zn (1.19), Mn (1.31), Cd (5.0 times) and on the contrary increased content of Pl by 5.6, Ni – 3.3 and Fe – 43.5 times. Providing of mares by Co is 54.7%, Cu – 88.5, Zn – 83.3, Fe – 88.4, Mn by 29%. The negative effect of Cobalt and Copper deficiency on erythrocytopoesis is shown. In particular, the number of erythrocytes, hemoglobin level, hematocrit value, and hemoglobin content in the erythrocyte indicate a development of alimentary anemia in pregnant mares. The established low level of Co and Cu that indicates the development of polymicroelementosis in mares. The Cobalt content in blood of non-pregnant mares was on the lower physiological limit and on average it was 0.48 ± 0.02 μmol/l. In the mares, at 7 month of pregnancy, the Cobalt content was lower (P < 0.01) than that of non-pegnant. In the 9–11 months of pregnancy, its level was on average 0.19 ± 0.02 μmol/l, which is lower by 2.5 and 1.9 times than in non-pregnant mares (P < 0.001) and at 4 months of pregnancy (P < 0.05). The Copper content in blood of mares at 9–11 months of pregnancy was lowest and the average was 2.09 ± 0.07 μmol/l (1.98–2.27), which is lower on 46.8 and 22.6% (P < 0.001) compared to non-pregnant and mares at 4 month of pregnancy. Hypocopperemia was established in 100% of studied mares. In non-pregnant mares, the Copper content was on average 3.93 ± 0.14 μmol/l. Taking into account the role of these microelements in metabolic transformations, changes in the composition of blood and the development of metabolism disorders in the organism of mares during the period of pregnancy can be explained.