Escherichia coli is an important cause worldwide of newborn and postweaning diarrhoea in pigs. Diarrhoea due to E. coli may and decreased weight gain. The aetiological agents of the disease are the enterotoxigenic strains of Escherichia coli (ETEC). These strains produce one or more toxins (LT, STa or STb) and present immunoglobulins block the adhesion function so that the bacterial attachment to the intestinal epithelium and, consequently, intestinal colonization are prevented. Additionally, the antibodies against the toxins neutralize their toxic effect on intestinal cells (Fairbrother, 2006).