[Concentration of selenium in the blood of young cattle in relation to age and season].

The concentration of selenium in the blood serum of heifers was studied for 22 months with special regard to the effect of age and year season. New-born calves were found to have a sufficiently high concentration of selenium (1.26 mumol/l). At weaning time the selenium concentration level was reduced significantly. The year season influenced serum selenium concentration levels and the reaction was positive during the grazing season. The lowest average values of serum selenium were obtained in the period from February to April (1.77 mumol/l).