Perinatal changes in the absorption of trace elements

Fetal demands for many of the essential trace elements change markedly during the terminal stages of development. Susceptibility to deficiency during early postnatal life is influenced by the extent of fetal trace element reserves, by inadequacies in the supply of some elements in maternal milk and by postnatal changes in the efficiency of trace element absorption. The efficiency with which essential and some toxic trace elements are absorbed after birth is a function both of age and of diet. Homeostatic mechanisms for the control of iron absorption are poorly developed in the newborn. There are indications that pinocytotic absorption of iron, copper, lead and cadmium may occur at this stage and account for the high efficiency with which these elements are absorbed from a liquid diet. Evidence of developmental changes in the enterohepatic recirculation of such metals is considered and an account is given of our very inadequate understanding of the processes of trace metal absorption in the weaned animal.