Storage of Vitamin A in Cattle

Abstract

Clinical symptoms of vitamin A deficiency were evident in two beef steers after 225 to 240 days on a ration of dried molasses beet pulp, rolled barley, cottonseed meal and calcium carbonate. Reserves were practically exhausted, and the animals were in critical condition after 282 days, at which time they were autopsied. The gradual depletion of reserves with advancing time was followed by estimating the vitamin A potency of the liver oil of steers autopsied after varying periods on the deficient ration, the Carr-Price color reaction being used. According to evidence presented, the carotene in the adipose tissue, which constitutes a part of the vitamin A reserve, may be withdrawn during vitamin A privation without coincident withdrawal of the depot fat. All the steers used had ample opportunity to store vitamin A before the experimental period. The expulsion of the fetus before it is viable, in the absence of infectious abortion, is described. Calves from heifers having a restricted intake of vitamin A during gestation developed a severe diarrhea at 2 to 8 days of age. The milk of the dams was shown to be deficient or subnormal in vitamin A. One calf exhibited marked night blindness although no clinical evidence of vitamin A deficiency has appeared in the dams up to 6 months following parturition. The liver tissue of mature beef cows, reared under favorable conditions, was found to have a concentration of vitamin A approximating that of high potency cod liver oil. The storage in the livers of newborn calves from cows receiving abundant vitamin A was found to be relatively low. Attention is called to the low concentration of vitamin A in the livers of calves at birth and to its high concentration in colostrum milk. This parallels the low concentration of globulins in the serum of newborn calves and their high concentration in the colostrum. In these experiments the manifestations of vitamin A deficiency occurring under natural conditions on the range, which were reported in previous publications (Hart et al., '33 a, '33 b) have been produced under controlled conditions. The relation of these findings to problems in range cattle in California is discussed.