Sensitisation of preruminant calves and piglets to antigenic protein in early weaning diets: control of the systemic antibody responses.

The immune response stimulated by dietary protein was studied in preruminant calves and piglets. Calves receiving dietary soya developed high serum titres of soya-specific IgG which did not decline with prolonged feeding. IgG1 and IgG2 subclasses showed a parallel rise although IgG1 predominated. Levels of antibody evoked by a combination of oral and parenteral sensitisation with soya protein were significantly greater than by parenteral sensitisation alone. These results suggest that the calves failed to develop oral tolerance. Passively acquired maternal soya-specific antibody did not influence the response to oral or parenteral sensitisation with soya. By contrast, piglets weaned onto a soya-containing diet became hyporesponsive to injection with soya protein. Thus, calves and piglets appear to differ in their ability to control adverse immune responses to dietary antigens. This could influence the severity of gastrointestinal disorders associated with early weaning diets.