Using nutrition to increase a cow’s defense against infection has been a recent area of research in recent years. As animal trace mineral status declines immunity and enzyme functions are compromised first, followed by a reduction in maximum growth and fertility, and finally normal growth and fertility decrease prior to evidence of clinical deficiency. A variety of reactive oxygen species (ROS) are produced by normal metabolic processes and by certain leukocyte populations during defense against disease. Oxidative cause damage of tissues and cellular components, and to reduce this, the diet should supplement with antioxidant (vitamin E and Selenium). Reproduction ability of leukocyte decreased because of insufficient Zinc. The antioxidant requirements of cows will likely increase as production demands continue to increase within the dairy industry. The objective of this study is to evaluate the effect of different levels of dietary Zinc, vitamin E and Selenium on immune responses efficiency of dairy cows during the transition period. For determine the optimum level of these micronutrients as one complex, 32 Holstein cows used in completely randomize design (CRD) with 3 different diet (10 cow used for treatment one, 11 cow used for treatment two and 11 cow used for treatment three). Treatment 1, 2 and 3 respectively were fed these micronutrients with recommendation of NRC, double of NRC and triple (3x) of NRC for 21 days to parturition until 21 days after it.NRC suggestion for these nutrients is: 0.3mg Se/kg DM, 80 IU vit E/kg DM and 30 mg Zn/kg DM for dry period and 0.3 mg Se/kg DM, 20 IU vit E/kg DM and 60 mg Zn/Kg DM for lactation. At parturition time and 21 days after parturition blood, colostrums and milk samples were collected and white blood cell, red blood cell and somatic cell count were measured in all samples. All data were analyzed with SAS (9.1) software. The total number of WBC in blood change considerably as parturition approaches in dairy cows. We detected a significant increase in the total number of WBC at calving. Cows in treatment 2 were shown improvement immune responses, decreases cases of diseases, having good status of SCC in colostrums and milk samples versus treatment 1 and 3. In addition, Dairy cows in treatment 2 significantly showed higher WBC concentrations in blood at calving in comparison with the other treatments (P 0.05). Treatments hadn’t significant effect on SCC in colostrums and milk, RBC concentration in blood samples. The cows in treatment 2 were had a lower production clinical diseases after calving in contract with treatment one (decrease 80% of diseases). These micronutrients and their interactions on immune responses continue to be an area of interest for research and production applications in future. The performance of high producing dairy cattle can be optimized to a certain extent by supplementing diets with
