Secretory IgA and antibodies to Escherichia coli in porcine colostrum and milk and their significance in the alimentary tract of the young pig.

Specific antisera prepared in rabbits against porcine immunoglobulins have been used in the measurement of IgG, IgA and IgM in porcine colostrum and milk throughout the first weeks of lactation. The immunoglobulins account for more than 60 per cent of the colostral whey protein and approximately 80 per cent of the immunoglobulin is IgG. During the first 2–3 days of lactation IgG and IgM fall to approximately one-tenth of the original level but IgA shows only a two- to three-fold decrease and becomes the predominant immunoglobulin in sow milk. Antibodies to 0141 and 08 antigens were predominantly associated with IgA although IgM is an important antibody in colostrum. Immunofluorescent studies of IgA in mammary tissue provide some evidence for local synthesis. The passage of sow milk IgA through the alimentary tract was studied in young pigs with re-entrant fistulae prepared in the small intestine. The observations are discussed in relation to the function of IgA as an antibody providing protection in the alimentary tract.