In the conditions of the Republic of Belarus there was studied the formation of nonspecific protection factors of the first year foals. By a principle of conditional analogues there was generated a group of clinically healthy foals at which monthly from bulbar veins there were taken tests of blood for hematological and biochemical analysis. From the obtained data it was visible, that within the first year of foal life there were taking place the processes of formation of nonspecific protection factors of an organism which were accompanied by a gradual increasing of quantity of erythrocytes, haemoglobin, leukocytes, certain change in the diagramme, and also increasing of bactericidal and lysozyme activity of blood serum. However, at seven-month age there was marked a considerable decrease in number of erythrocytes, leukocytes, concentration of haemoglobin, bactericidal and lysozyme activity of blood serum is marked, in leukogram share reduction of segmented neutrophils, and at the same time, the content of eosinocytes and lymphocytes increased. It testified the decreasing of protective forces of an organism during this period. Consequently, the seventh month in the postnatal period of foal life proved to be the most critical.

In the conditions of the Republic of Belarus there was realized a study of age-specific features of level of erythrocytes, haemoglobin in blood, activity of aspartate aminotransferase, alanine aminotransferase, lactate dehydrogenase, alkaline phosphatase, as well as concentration of calcium, phosphorous, magnesium and ferrum in blood serum of suckling colts in the first 6 months of life. In the studied animals there was stated increased levels, haemoglobin and ferrum concentration in blood, but during the 6th month of life the same indexes decreased considerably. The most considerable changes оf blood serum enzymatic activities occurred at the age of 2 and 6 months. Thus, during the 2nd month of life a raise in ALAT, LDH activity, calcium and phosphorus concentration was noticed. At the age of 6 months ALAT and ASAT levels increased, and LDH activity, magnesium and phosphorus concentration decreased. During the first 6 months of life the ALP activity was on a high level and underwent no reliable changes. As the research showed, blood serum enzymatic activity and concentration of calcium, phosphorus, magnesium and ferrum depended on colt age and change at the process of growth and development of animals.