Postnatal Adaptation

Directly after birth, the piglet takes up macromolecules from the intestinal lumen in a nonselective way. IgG from the sow's colostrum is transported into the organism of the newborn via enterocytes (Komuves et al. 1993; Komuves and Heath 1992). A rapid "closure" of the gut for the macromolecule uptake occurs within 24 and 48 hours after birth (Leece 1973). Colostral intake is essential for efficient immune reactions, and the germ-free colostrum-deprived "virgin" piglet can serve as model for the assessment of the development of defense against toxins (Lee et al. 1998). Lymphocytes migrating into the lactating mammary gland obviously provide the immunolog-ical information necessary for the production of secretory IgA that is released into the sow's milk for maintenance of humoral immunity in the offspring (Salmon 2000).

Ovalbumin-fed animals were used to follow antigen uptake by the sow and transfer of antigen and specific antibodies to the offspring via colostrum (Telemo et al. 1991). After antigen feeding during gestation and lactation, the antigen was tolerated by the piglets; however, antigen feeding during lactation alone resulted in induction of IgG antibody production and diarrhea (Bailey et al. 1994b). These experiments demonstrate the immunological competence of the porcine fetus and newborn against environmental antigens. The immune response may be tolerance or defense against the antigen. In lymph duct cannulation experiments in young pigs, the nutritional uptake of antigens was described (Kiriyama et al. 1988).

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