EN
The role of leucocytic infiltration into milk in destructing pathogenic flora introduced into mammary gland is well known (3, 5, 6). It has been proved, too, that the number of leucocytes passing from blood into milk need not be too high for effective counteraction against proliferation of microorganisms at their single intramammary introduction (7). It was observed in the previous works (8, 9) that phagocyting activity of milk leucocytes from mammary gland in subclinical inflammation state was lower than phagocyting activity of blood leucocytes of the same cow; similar observations were made in relation to the opsonins level. In the present work it has been decided to investigate phagocyting activity of leucocytes of cow milk during acute mastitis stimulated by different factors. The observations concerned also opsonins level in milk and serum and the rate of phagocyting microorganisms introduced into milk.