Transport of passive immunity to the calf

Abstract

The protective effects of colostrum in the newborn calf appear to be directly associated with the immunoglobulins IgG, IgM, and IgA. The exact role which these colostral components play in protection is still in debate. The transport of intact immunoglobulins from the intestine into the circulation of the calf is dependent on the lining intestinal epithelial cells. These cells are characterized by the capacity to engulf large molecular weight proteins, maintain them within a vacuole during transport, and release them at the basal cell membrane into the lamina propria. The ability of the intestinal epithelium to transport proteins is decreased approximately 56% during the first 24 hours after birth. This process referred to as “closure” does not appear to be absolute, since bacterial antigens may be absorbed throughout the life of the animal. Enhancing immunoglobulin absorption or prolonging neonatal permeability of the intestine would appear to be an approach in insuring adequate levels of passive immunity. The efficiency of absorption of immunoglobulins is due largely to the amount of immunoglobulin consumed, however, other factors such as deficient absorption and/or immunoglobulin in colostrum also must be considered.