Recently, we demonstrated the presence of IL-1 beta in the colostral whey from dairy cows. Here, authors examined oral transmission of colostral IL-1 beta and its immunological effects on the neonatal calves. Biotin-labeled recombinant bovine (rb) IL-1 beta was administered orally to newborn calves and monitored in the serum. The results disclosed the passive transfer of colostral cytokines via the oral route, and a potent increase in white blood cell (WBC) count was observed in all calves administered with rbIL-1 beta. Oral administration of IL-1 beta significantly increased the proliferation of peripheral blood mononuclear cells (PBMCs) stimulated with concanavalin A, and the O(2)(-) production of stimulates neutrophils in newborn calves. These results suggest that the oral administration of IL-1 beta has an immunostimulatory activity in the newborn calf.