The aim of this research was to determine the effect of dietary selenium supplementation (organic, inorganic) to high pregnant and lactating ewes on the production performance and exterior characteristics of their lambs. The research included 30 pregnant Merinolandschaf ewes and lambs. The control group of ewes and lambs ration (group I) was composed of 300 g/day/animal feed mixture without the addition of selenium and 150 g/day/animal, barley and alfalfa hay which they had ad libitum. Feed mixture of group II was supplemented with 0.3 mg/kg of Selplex®, and the third group with the same amount of Sodium selenite. The average body weight of lambs at the age of 23 days was significantly (P<0.05) bigger in the group given inorganic selenium in comparison to the control group. Addition of inorganic (P<0.01) or organic (P<0.05) selenium led to a significantly better exterior characteristics in lambs at the age of 63 days comparing them with the control group of lambs. A significant by (P<0.05) better indices of body proportions and body mass are evident in younger lambs whose mothers, and they, were fed mixtures with the addition of inorganic selenium. Indexes of anamorphosis, body condition and massiveness were better (P<0.05) in older lambs which had organic form of selenium added to feed mixture. Results of current study suggest that the form of Se source used in this research, has a limited potential for improving the production performance of lambs especially if there was no significant lack of seleniumCilj ovoga istraživanja bio je utvrditi utjecaj dodatka selena (organskog, anorganskog) u krmnu smjesu visoko gravidnih ovaca i ovaca u laktaciji na proizvodna svojstva i eksterijerne odlike njihove janjadi. Istraživanje je provedeno na 30 Merinolandšaf ovaca i janjadi. Obrok kontrolne skupine ovaca i janjadi (skupina I) bio je sastavljen od 300 g/danu/životinji krmne smjese bez dodatka selena te
150 g/danu/životinji ječma i sijena lucerne kojeg su imale ad libitum. U krmnu smjesu II skupine dodano je 0,3 mg/kg Selplexa®, a u treću ista količina natrij selenita. Prosječna tjelesna masa janjadi u dobi od 23 dana bila je značajno (P<0,05) veća u skupini s dodatkom anorganskog selena u odnosu na kontrolnu. Dodatak anorganskog (P<0,01) ili organskog (P<0,05) selena vodi značajno boljim eksterijernim odlikama u janjadi prosječne dobi od 63 dana u odnosu na kontrolnu skupinu janjadi. Značajno bolji (P<0,05) indeksi tjelesnih proporcija i tjelesne mase utvrđeni su u mlađe janjadi čije su majke a i oni imali dodatak anorganskog selena u krmnoj smjesi. Indeksi anamorfoznosti, tjelesne kondicije i mišićavosti su značajno (P<0,05) bolji u starije janjadi čije su majke a i oni imali dodatak organskog selena u krmnoj smjesi. Rezultati upućuju da izvor selena u krmnoj smjesi u ovom istraživanju ima ograničavajući potencijal u poboljšanju proizvodnih svojstava janjadi osobito ukoliko prethodno nije prisutan veliki nedostatak, već samo manjak selena
