Supplementation of dairy cows with selenized yeast during the last 8 weeks before parturition has been shown to improve selenium and IgG status of their offspring. Agricultural biofortification is an efficient, cost-effective method for selenium supplementation of cows and their offspring. In this study, we evaluated the effect of feeding sodium-selenate fertilized alfalfa to dairy cows during the close-up period on selenium status, immune function, and performance of their offspring. After blocking for breed, 12 dairy heifers (6 Holsteins and 6 Jerseys) were randomly assigned to 2 groups. One group received 1 kg DM alfalfa enriched with Se (3.2 mg/kg DM)/100 kg of BW mixed with TMR or the same amount of alfalfa with a standard Se level (0.4 mg/kg DM) for 40 d before parturition. Calves received their mother’s colostrum and were monitored for BW at calving, ADG and health status. Whole blood samples from calves collected at 1 and 24 d of life were used to assess Se, Co, Zn, and Cu level using ICP-MS and white blood cells count (WBCC), leukocytes differentials (LD), and phagocytosis. Data were analyzed using proc GLIMMIX of SAS with treatment, breed, and time and their interactions as main effects. Feeding selenium enriched alfalfa vs. low selenium alfalfa to pregnant heifers increased (P < 0.05) Se Se (149.1 vs. 207.3 ng/mL), Co (0.34 vs. 0.54 ng/mL), and Cu (872 vs. 948 ng/mL) in whole blood of their offspring, indicating a synergistic effect of Se on utilization of other trace minerals. Overall, the Se was higher in Jersey vs. Holstein calves (203.87 vs. 147.5 ng/mL, P < 0.05). BW, ADG, health status, WBCC and LD were not affected in calves by the treatment of their dams. Higher rate of phagocytosis (P < 0.05) was detected in calves born from cows supplemented with high selenium vs. low selenium, indicating a better immune system in the former vs. the latter. Our data indicate that agricultural Se biofortification of dairy cows during the close-up period is an effective and cost-efficient management tool to improve the level of Se and other trace minerals in whole blood and the immune capacity in their offspring without adversely affecting their performance.