The influence of colostral leukocytes on the immune system of the neonatal calf. II. Effects on passive and active immunization.

The influence of colostral leukocytes on the concentration of immunoglobulins and antibodies against an enterotoxigenic strain of E. coli in the sera of newborn calves was investigated for four weeks using four experimental groups. The calves received either complete colostrum (COL-, n = 16), cell-supplemented milk substitute (MS+, n = 7) or pure milk substitute (MS-, n = 6) during the first three days of life. The cows were not specifically immunized. The sera of the COL+ calves had significantly higher concentrations of antibodies against E. coli mainly of IgG1 specificity on the second day of life as compared to those of the COL-. The sera of the COL+ calves contained significantly more IgM on days 2 and 5 and slightly more IgA during the first week. Both COL groups had equal concentrations of serum IgG. It appears that colostral leukocytes which are an integral part of the colostrum enhance the passive immunity of the neonatal calf, especially in regard of antibodies and immunoglobulin classes which are essential for intestinal immunity. The concentration of IgM in the sera of the MS+ calves was reduced, that of IgG did not rise to appreciable amounts; the IgA synthesis started one week later as compared to the MS- group. The administration of isolated colostral cells led to an impairment of the natural active immunization.