effects of different levels of selenium on performance, blood parameters and nutrient digestibility in mehraban male lambs

two experiments were conducted to evaluate the different levels of selenium supplements on performance, blood metabolites and nutrient digestibility in mehraban male lambs. the first experiment consisted of 18 lambs, 4-5 months of age and 35.9±2.7 kg average in weight randomly allotted to 3 treatments. treatments were: 1) control diet (a diet without selenium, containing 0.06 ppm of selenium), 2) control diet + 0.2 ppm se as sodium selenite and 3) control diet + 0.4 ppm se as sodium selenite. this trial lasted for 70 days. blood samples were taken on days 0, 35 and 70. in the second experiment, 4 lambs were randomly selected from each treatment group and moved to digestibility boxes to evaluate the effects of different selenium levels on apparent nutrient digestibility. the experiment continued for 18 days with the first 12 days as the adaptation period plus 6 days of sampling. the trial were carried out as a completely randomized design. supplementations of selenium to diet did not have significant effect on lambs performance. there were no significant differences in concentrations of plasma minerals, serum lipid profile and apparent nutrient digestibility. the serum level of tetra-iodothironine (t4) were decreased significantly. furthermore, supplementation of selenium increased serum tri-iodothironine (t3) level and whole blood gpx activity. overall, the results of this study showed that requirement of growing mehraban lambs, met with 0.2 ppm selenium.