EN
The studies started on 40 sheep at the age of 7 months infested by gastro-intestinal nematodes, and ended after lambing. Group I received Vita-E-Selen at a dose of 0.1 mg/kg b/w, group II was treated with Systamex at a dose of 7.5 mg/kg b/w, group III was given both the preparates and group IV (untreated) served as a control. The selenium and Systamex preparáte were applied at sexual puberty, before mating, at the 1 week of pregnancy, 7 days before lambing and on day 7 after weaning. The application of Vita-E-Selen, Systamex or both preparates decreased extensiveness of invasion of gastro-intestinal nematodes from the Trichostrongylidae and Ancylostomatidae families. The preparates did not affect activity of aspartic aminotransferase, alanine aminotransferase, level of cholesterol and urea in blood plasma.