The aim of this research was to determine the influence of 56-days (from day 4 to day 60 post partum) of simultaneous supplementation of selenium (Se) and iodine (I) enriched Chlorella algae on blood and urine Se concentrations and thyroid hormone levels in ewes and lambs. The study included 18 Šumava sheep ewes and their lambs divided into three groups (CON, HSe, HSeI). Selenium and I content in the diet of ewes measured 0.2 and 0.7 mg (CON), 0.4 and 0.7 mg (HSe), 0.4 and 1.3 mg (HSeI) per kg of dry matter. During the experimental period a significantly higher blood serum Se concentration was determined in ewes of the HSeI group (P< 0.001) and urine (P< 0.01). A significantly higher (P< 0.001) blood serum Se concentration was found also in lambs of the HSeI group. The highest Se concentration in the blood serum was recorded in ewes (128.0 μg/L) and lambs (74.2 μg/L) on the 26th day of the experiment. The results demonstrate a higher utilization of Se administered in the organic form accompanied by a higher intake of I applied also in the organic form. Plasma thyroid hormone levels in ewes were not explicitly affected by higher Se and I supplementation. A higher Se concentration in the lambs’ blood serum led to significantly higher (P< 0.05) T3 levels up to 30 days post birth.
