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 studied the nonspecific resistance of lambs of Latvian Black Face breed during the colostrum and milk fed period of their growth development. In course of the experiment there were used 10 newborn lambs. Analysis of resistance was realized in accordance with a scheme: before colostral milk sucking; in 6, 12, 24 hours; in 3, 7, 14, 21 days; in 1, 2 and 3 months after birth. In lambs during the colostrum and milk fed period of growth there were marked two critical periods, which were characterized by low indicators of resistance: before colostral milk uptake and at 7-21 day-old age. Increasing of leukocytes, bactericidal, lysozymic activity of blood serum, phagocytal activity of leukocytes, crude protein and antibodies in the first days of lamb life took place due to their entrance in blood with colostral milk, just because at this time the intestines wall possessed ability to transit in native condition the antibodies, enzymes, and leukocytes. At 7-21 day-old age in connection with reduction of these factors quantity of in colostral milk, and also due to reduction of intestines capacity, their was stated that their entrance in blood of newborn lambs decreased, but at 3 month old age of lambs there were stated to form internal protective factors of resistance because of which their quantity in blood started to increase.