Blood biochemical indicators and concentration of thyroid hormones in heavily pregnant and lactating ewes depending on selenium supplementation

The aim of this research was to determine the effect of dietary selenium supplementation (organic and inorganic) on the biochemical indices and thyroid hormone concentration in the blood of heavily pregnant and lactating ewes. Research was conducted on 30 pregnant ewes of the Merinolandschaf breed divided into 3 groups, and lasted for four months (two months on ewes in late pregnancy and two months on ewes during lactation). The first group was given a basal diet without the addition of selenium. The feed mixture of group 2 was supplemented with 0.3 mg/kg of organic sources of selenium, and group 3 with the same amount of inorganic sources of selenium. In lactating ewes, organic and inorganic selenium lead to a significant (P < 0.05; P < 0.01) increase in urea concentration. At the same time, in lactating ewes inorganic selenium had a significant decreasing effect (P < 0.05; P < 0.01) on cholesterol, low-density lipoprotein and triglycerides. Organic selenium in heavily pregnant ewes significantly (P < 0.01) increased aspartate aminotransferase activity in comparison to group 1 and 3. In lactating ewes significant (P < 0.05) differences in aspartate aminotransferase activity were determined between groups 2 and 3. With selenium supplementation a significant (P < 0.01; P < 0.05) increase concentration of Se was determined (for heavily pregnant and lactating ewes, respectively), as well as Na, Cl, Fe (lactating ewes), and a decrease of K (high pregnant ewes). Organic selenium had an effect on the increase of triiodothyronine in lactating ewes. We can conclude that selenium supplementation contributes to good health and condition of ewes in the demanding period of lactation.