Effect of immunising pregnant sows with different Escherichia coli vaccines on the antibody levels in the piglet sera.

Six groups of pregnant sows were immunised with four different commercial Escherichia coli vaccines. Five groups were vaccinated parenterally while the other group was vaccinated orally and then parenterally. The colostral antibody titres to E coli O149 K91(B) K88 as measured by indirect haemagglutination were significantly higher in the vaccinated sows than in the controls. Oral priming by vaccine feeding as opposed to parenteral administration did not appear to produce an anamnestic response. Antibody levels in the piglets born to vaccinated sows were higher than in those born to control sows. Nevertheless a substantial proportion of piglets born to all sows had very low levels of passively acquired immunity.