Bactericidal antibody studies in maternal serum, colostrum, and newborn serum of the pig.

The development of natural bactericidal antibody levels in the piglet was studied and bactericidal antibody levels in newborn serum, maternal serum, and colostrum of the pig were determined. Natural bactericidal antibody levels in serum of the newborn piglet before ingestion of colostrum were extremely low and, as in adult serum, dependent upon natural antibody and complement for its activity. When the animals were 1 year old, large variations in natural antibody levels were found in those of a single litter. The levels of natural antibody in maternal serum, colostrum, and precolostral newborn serum did not reveal a positive correlation. Finally, immunization of gilts before delivery provided a very effective antigenic stimulus in the piglets whose antibody titer, when the animals were 2 weeks old, was comparable to that of the immunized parent.