Absorption of Colostral Immunoglobulins in Newborn Calves

Passive immunity to some infectious agents is transferred from the cow to calf via colostrum. Transfer is by an apical tubular system in the intestinal absorptive cells for a limited time after birth. Uptake of macromolecules into the cells appears to be nonselective; however, some substances are not transferred to the blood. Cessation of transfer of material from the epithelial cells to blood occurs spontaneously at a progressively increased rate after 12 h of age with mean closure time at approximately 24 h. Proportions of the different classes of immunoglobulins in serum of calves after ingestion of colostrum reflect the proportions in colostrum when absorption is completed.