A completely randomized design experiment consisting 5 treatments with 5 replicates (6 birds per replicate) was carried out by allotting 150 white Lohman laying hens at 18 weeks old. The experimental diets were prepared by addition of different levels of E-selenovit supplement (0.0, 35, 65, 80 and 100 mg / kg of feed) to the diets. The diets were isonitrogenous and isocaloric and of fered ad libitum for 12 weeks. The hens performance including hen-day egg production % , feed intake, egg mass (g/hen/day) and feed conversion ratio (FCR, g feed: g egg) was measured. Antibody production against Sheep Red Blood Cells (SRBC) and Newcastle Disease Virus (NDV) also was measured. The results indicated that inclusion of E-selenovit had a significant effect on performance (P<0.05). Supplementation of diets with E-selenovit significantly increased feed intake and improved feed efficiency (P<0.05). Egg production was higher in treatment five than that of control, (94.3 vs 88.1 respectively). Egg mass also significantly affected by inclusion of E-selenovit (P<0.05). Higher egg mass was observed in treatment five than treatment one (54.9 vs 50.7). Addition of E-selenovit significantly increased (P<0.05) antibody titrations against SRBC and Newcastle disease and it was higher in treatment five compared with control group,( 8.03 vs 6.33 and 8.93 vs 6.31). These results showed that Eselenovit supplements can improve immune response of laying hens under heat stress condition and a more positive effect was observed when 100 mg/kg E-selenovit added to the diet.
