ABSTRACT
Colostral immunoglobulin is not essential for human and other primate neonates because the haemochorial placentation of these species permits transfer of maternal immunoglobulin across the chorionic epithelium, such that the neonates are born with serum IgG concentrations approaching those of the adult. In contrast, in dogs and cats the additional barrier of the maternal endothelium in endotheliochorial placentation permits transfer of only a small quantity of IgG. Therefore, pups and kittens may be born with only 5% or less of the level of serum immunoglobulin present in the adult. Even greater barriers characterize the syndesmochorial placentation of the ruminant and the epitheliochorial placentation of the horse, such that there is no possibility for maternal transfer of immunoglobulin in utero in these species. As a consequence, the colostrum of animals has significantly different composition to that of the milk.
