Prenatal and postnatal development of immune system in ruminants

The development of the immune system in ruminants begins at the early stages of fetal life. In late pregnancy, the fetus is capable of immune response against foreign antigens. The primary lymphatic organ for B lymphocytes is the ileal Peyer's patch. High susceptibility of young ruminants to infections is related to the failure of passive transfer (FPT). FPT or a partial failure of passive transfer (PFPT) may be caused by different factors depending on the newborn, the dam or the human. The understanding of the function of the neonatal immune system and its differences from the adult immune system should help in avoiding husbandry mistakes and in protecting the animals' health.