The Effect of Supplementation on Selenium and Zinc Content in Blood and Milk of Dairy Cows

Milk is an important source of microelements for calves during the suckling period as well as in human nutrition. Concentration of trace elements in blood and their secretion via milk can significantly change depending on food intake and composition. Proper control of selenium and zinc content in blood and in milk can improve the status of these microelements, so that the occurrence of deficiency or excessive quantity due to their increased intake can be prevented. This paper presents the results of the study on the concentration of selenium and zinc in the blood and milk of diary cows whose rations have been supplemented by organic forms of selenium (0.2 mg/kg DM) and zinc (40 mg/kg DM) during the last ten days of dry period and early lactation. Supplemented cows in trial groups A and B achieved significatly higher concentrations of these microelements in blood (Se 186.70±8.50 µg/L vs. 118.80±7.05 µg/L), blood serum (Zn 1204.70±109.5 µg/L vs. 1095.40±130.2 µg/L) and milk (Se 57.30±8.05 vs. 21.30±4.60 µg/L; Zn 2893.90±120.15 µg/L vs. 1952.10±130.50 µg/L) on 60th day postpartum compared to non-supplemented control