FACTORS AFFECTING THE DURATION OF INTESTINAL PERMEABILITY TO MACROMOLECULES IN NEWBORN ANIMALS

Summary 1. In several species, partial, or even complete passive immunization of the offspring is achieved through maternal antibodies which are concentrated in the colostrum. Failure to obtain sufficient colostrum renders newborn farm animals highly susceptible to systemic and enteric infection with E. coli. 2. A significant number of colostrum‐fed calves nevertheless develop colisepticaemia and many of these animals are hypo‐ or even agammaglobulinaemic. A premature termination of intestinal ability to absorb colostral antibodies (closure) may be responsible for some of these cases. 3. Pharmacological doses of certain exogenous corticosteroids are capable of inducing premature closure in rats. It is not certain though whether exogenous corticosterone can induce precocious closure in rat pups or whether exogenous corticosteroids can induce closure in members of other mammalian orders. Corticosteroid levels, however, may influence the efficiency of immunoglobulin absorption. Attempts to delay closure with adrenal suppression in animals with short immunoabsorptive periods have not been effective. 4. In piglets, but not in puppies or calves, starvation can postpone closure for several hours and consumption of food may be necessary before closure can occur. 5. Closure in the rat and pig apparently takes place by different methods.