We evaluated the effect of a commercial bovine colostral whey on the complement-mediated immune responses of calves. Two groups of neonatal calves were fed, in addition to whole milk (WM) and pooled colostrum (PC), different amounts of a commercial immunoglobulin concentrate made from pooled colostral whey (Ig-C) for the first two feedings post natum. The control group was fed WM and PC only. Serum samples were obtained at the ages of 2, 7, 14 and 30 d. Bacteriolytic activity against complement-sensitive Escherichia coli JM103 and opsonic activity against complement-lysis-resistant E. coli IH3080 strains were studied, as well as the levels of C3 complement component and E. coli JM103 specific antibodies in the sera.

Groups fed Ig-C had 2–3 times higher bacteriolytic activity than the control group of both the classic (P < 0·005) and alternative pathways (P < 0·0001) at days 2 and 7 post natum. This effect is obviously not caused solely by the antibodies ingested but also involves other unknown colostral factors, possibly lectins. The opsonisation capacities of the sera correlated well with the amounts of immunoglobulins ingested (P < 0·05) at days 2–14. The levels of C3 component in sera did not differ between the groups. In the group fed the largest amount of immunoglobulins levels of E. coli JM103-specific antibodies were highest (P < 0·0001). It can thus be concluded that the antibody independent complement activities of serum can be increased substantially by feeding colostral whey concentrate to calves during their first days of life.