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The Absorption of Vitamin A Natural Esters and of Carotene by Young Male Holstein Calves¹

Pennsylvania Agricultural Experiment Station, State College

ABSTRACT

The concentrations of vitamin A and carotene in the digestive tract contents and tissues after a single administration of either compound at a high or low level to young calves have been studied. Further observations were made with respect to the effect of such administrations upon liver storage and upon blood plasma carotene and vitamin A.

The resulting data indicate that the most active absorption of vitamin A takes place in the upper two-thirds of the small intestine. The concentration of vitamin A in the digestive tract contents after the administration of one single dose was lowest in this area. The mucous tissues of the upper two-thirds of the small intestine were more concentrated with vitamin A than those elsewhere. A highly significant correlation coefficient was calculated between the increase in blood plasma vitamin A and the concentration of vitamin A in the mucous tissue of the small intestine after the administration of a single dose of vitamin A. Absorption seemed to be limited in the lower one-third of the small intestine and in the large intestine, since there appeared to be a concentration effect upon the vitamin A that passed into these two sections.

The low concentration of carotene in the middle one-third of the small intestine after a single administration of this compound might indicate that absorption takes place most rapidly in this area. The low concentration of carotene in the tissues of the digestive tract wall may be evidence of carotene conversion, but concurrent increases in vitamin A could not be demonstrated under these conditions.

A large single dose of vitamin A or of carotene did not affect liver storage of vitamin A during the 8-hr, period following administration. The administration of vitamin A in a single dose increased blood plasma vitamin A in all instances but one. Carotene administrations resulted in inconsistent and relatively small changes in blood plasma carotene and vitamin A in these experiments.

¹ Data contained in this publication are from a thesis submitted by the senior author to the Graduate School of The Pennsylvania State College in partial fulfillment of the requirements for the degree of Doctor of Philosophy. Authorized for publication as paper no. 1681 in the Journal Series of The Pennsylvania Agricultural Experiment Station.

² Present address: Department of Dairying, Oklahoma A. & M. College, Stillwater, Okla.