Systemic and local gut-specific antibody responses in preruminant calves sensitive to soya

The systemic and local (gut) patterns of antibodies against various proteins from soyabean were analysed in preruminant calves fed milk substitutes based on skim milk powder ( smp) or heated soyabean flour ( hsf) as the main protein sources. The titres of IgM, IgA, IgG 1 and IgG 2 antibodies were determined against feed extracts and purified soyabean proteins by dot-blotting in plasma after three months and jejunal mucous secretions after six months of feeding the experimental diets. The calves fed hsf had higher levels of circulating IgA, IgG 1 and IgG 2 antibodies against raw or heated soya extracts and purified proteins including αonglycinin, β-conglycinin, Bowman-Birk protease inhibitors and lectins than the calves fed smp. In contrast, the differences between the IgM titres of the groups were most often not significant. The patterns of specific antibodies present in the jejunum were broadly similar to those observed in the blood, although the differences between the groups of calves more often reached significance for IgG 2 and IgM than for IgA and IgG 1, when the purified soyabean proteins were considered.