The demonstrated effect of MOS on immunoglobulins (Ig) in poultry and piglets implies that more immunoglobulins could be available in the colostrum of sows supplemented with MOS. Colostrum represents the accumulated secreted antibodies of the mammary gland. In pigs, placentation is epithelichorial, which means that the fetal chorionic epithelium is in contact with intact uterine epithelium. In animals with this type of placenta, transplacental passage of immunoglobulin molecules is totally prevented. This makes the newborn piglet entirely dependent on antibodies received in the colostrum. The sow colostrum is rich in IgG and IgA, but levels of IgG drop rapidly and IgA predominates in the milk as lactation proceeds (Curtis and Bourne, 1970). In the pig, protein absorption seems to be selective with IgG and IgM preferentially absorbed. Improving the overall immunoglobulin concentration of colostrum may provide benefits to the young piglet in two ways.