Selenium is a trace mineral with antioxidant proprieties, which, by mediating  the glutathione, indirectly protects the hemoglobin against the risk of oxidation by peroxides through three antioxidant enzymes: superoxide dismutase (SOD), glutathione peroxidase (GSH-Px) and catalase The experiment was done on 20 laying chicks from the Rosso race, 6 weeks old at the start. The chicks were divided in 2 batches, and one of the batches received feed enriched with organic selenium (Sel-Plex). After 180 days, biological samples were colected by cubital vein puncture and hematological and biochemical determinations were made. The results were tabled, graphically represented and biostatistically interpreted. In the experimental batch significant growths were observed in the erythrocyte constants: erithremie, hemoglobinemy, hematocrite and MCH. Of the biochemical markers significant growths were observed in: ascorbinemic acid, alkalin phospahasis and selenium. The following parameters dropped significantly : proteinemia, amylase and MCV. Changes were also observed in cholesterol, calcium, magnesium and other parameters, but without statisticaly value. In the present paper we have shown the beneficial role of organic selenium on some haematological and biochemical markers, resulting in a growth of erythropoiesis, and at the same time a intensification of the metabolic processes in the experimental group.