This thesis investigated the impact of complete replacement of inorganic sources of supplementary trace minerals by organic sources in the diet of transition cows on cellular and humoral immunity of dams and neonate calves, colostrum characteristics, and oxidative balance, health and growth of calves. In cows, neu-trophil function was assessed in vitro by flow cytometry assays, and acquired immunity was evaluated by in vivo IgG responses to ovalbumin. In calves, passive transfer of immunity was assessed at 24 h after colos-trum feeding, and neonatal cellular immunity was evaluated by cytokine responses to ex vivo LPS stimula-tion of whole blood. The replacement strategy enhanced postpartum phagocytosis intensity of neutrophils in cows, increased concentration of Se in colostrum and in serum of female neonates, increased basal concen-trations of effector cytokines (IFNγ and IL4), enhanced secretion of β-chemokines (CCL2, CCL3) upon stimulation with LPS, and tended to improve preweaning health of female calves.