[The effect of the season of the year and the stage of pregnancy on selenium levels in the blood of sheep].

During one year selenium dynamics in the blood serum of 19 sheep was studied in relation to the degree of gravidity. Seasonal character of selenium dynamics with a positive reaction was demonstrated during the period of grazing, and a dependence of selenium serum concentration on the degree of gravidity was also proved; the highest mean value of selenium was recorded in ewes in the seventh month of gravidity (3.67 mumol.l-1). Delivery and onset of lactation reduced negatively selenium concentrations in the blood serum to the lowest selenium levels (2.15-1.89 mumol/l-1).