Serum IgG and IgM responses to sheep red blood cells (SRBC) in weaned calves fed milk supplemented with Zn and Cu.

Because ruminants have a syndesmochorial placenta, the neonates are agammaglobinaemic and prone to morbidity and mortality from opportunistic infections. Only temporary benefit in passive immunity transfer from mother to offspring is derived from feeding colostrum to neonates. The serum immunoglobulin (Ig) G and IgM responses to challenges with sheep red blood cells (SRBC) were investigated in calves fed milk supplemented with zinc, copper, or both. Twenty crossbred calves, weaned on day 5, were divided into four equal groups and fed for 75 d. Group T1 was fed milk alone; group T2 was fed milk supplemented with 25 ppm Cu; group T3 was fed milk supplemented with 100 ppm Zn; and group T4 was fed milk supplemented with 25 ppm Cu and 100 ppm Zn. The antigenic challenges with SRBC were made on days 35 and 65. Serum IgG and IgM levels were measured at day 30 and at 2-wk intervals thereafter in collected blood samples. Blood zinc and copper levels and superoxide dismutase (SOD) activity were also measured periodically. Higher IgG and IgM responses were observed in groups T3 and T4 (the zinc-supplemented groups). The responses were higher after second challenge with SRBC. The changes in blood copper and zinc concentrations and SOD activity were in accordance with the type of supplementation. The results suggested that the zinc-supplemented groups in particular showed a stronger humoral immune response, probably as a result of the beneficial effect of zinc on the interaction between T helper cells and B cells.