The importance of colostral immunoglobulins and their absorption from the intestine of the newborn animals.

It is well established that there normally is no transmission of maternal immunoglobulins across the placenta of the pig and calf. The passive transfer of colostral immunoglobulins from mother to neonate is for pig and calf the most important way of giving immediate immunological protection. The proteolytic activity in the digestive tract is low, and is further minimized by the presence of trypsin inhibitor in colostrum. The small intestine is lined with highly vacuolated, immature mucosal epithelial cells which are capable of absorbing macromolecules. Immunoglobulins in the lumen of the intestine are first internalized by enterocytes via pinocytosis in the uptake phase, and internalized macromolecules are thereafter transported to the blood. In pig and calf, the uptake and transport of macromolecules is qualitatively nonselective, including a variety of homologous and heterologous proteins. The absorption of immunoglobulins has dropped to a relatively low level after 24-36 hours. What regulates closure is not fully known, but appears to be controlled by endocrine influences and coordinated with the development of the enzymes that characterize the mature microvillus surface. Many factors influence the absorption of colostral immunoglobulins in the newborn e.g. starting age of colostrum feeding, feeding before colostrum feeding, amount of colostrum fed, concentration of immunoglobulins in colostrum, exposure to stress, permeability changes in the intestine.