From several experiments on selenium metabolism in order to measure the effect of selenium supplementation (0, 2, 4, 8, 12 and 16 mg daily under selenite form), haematological, biochemical and mineral parameters were studied and their interactions with selenium status and dietary selenium were analyzed. Considering the increasing level of supplementation, important changes in blood parameters were observed: significant decreasing of PVC, haemoglobin and iron concentration attesting the sign of anaemia from 8 mg level.  An important decrease of blood albumin and a drastic fall of uraemia expressed the loss of appetite in intoxicated animals receiving at least 12 mg selenium daily. At reverse, the enzymes attesting cell damage increased significantly. The decreasing of zinc and the increasing of copper from 8 mg showed inflammation process in target organs. It was concluded that se selenium supplementation could not overpass 4-8 mg per day for adult animals or 0.5-1 ppm in the diet.