Effect of Vitamin A Depletion on Liveweight, Plasma and Liver Levels of Vitamin A and Microanatomy in Young Dairy Calves

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Abstract
Bureau o1" Dairy Industry, Agricultural Research Administration, U. S. D. A., Washington~ D. U. A quantitative assay of the vitamin A stores, not involving sacrifice nor cans- ing clinical or pathological changes is needed to evaluate different dietary sources and ways of administration of vitamin A and carotene fed to young dairy calves. The possibility of feeding calves a vitamin A-free ration for relatively short periods of time, accompanied by determinations of blood plasma levels of vitamin A to predict vitamin A stores has not been fully explored. Moore and Berry (9) observed differences in plasma vitamin A levels in two groups of calves placed on a carotene-free ration at 90 days of age and previously fed either clover and timothy or lezpedeza hays. Blood plasma vitamin A levels have been used as criteria to determine the utilization of fetal storage of vitamin A in newborn calves fed a ration of skimmilk (2). In addition, the time for the blood plasma vitamin A to reach 4 ~ per cent in calves placed on a vitamin A- deficient ration after 90 days of age has been correlated with the vitamin A in- take from birth to 90 days of age by Jacobson et al. (6). A relatively constant percentage decrease in liver stores of vitamin A in yearling steers fed a low carotene ration was demonstrated by Frey and Jensen (5). The objectives of this experiment were to study in particular the effect of feeding a vitamin A depletion ration on the blood plasma levels of vitamin A and carotene and, secondarily, the effect of such a ration on liver levels of vita- min A, liveweight changes and microscopic anatomy in young rapidly growing dairy calves. E~PERIMEI~'TAL Animals. Fourteen male and three female Holstein calves and four male Guernsey calves at 106 days of age were placed on experiment during the months of February through May, 1950. Fifteen of these calves, all Holsteins, had previously been fed one of three types of alfalfa hay. The detailed dietary and managerial history of these calves up to 106 clays of age appeared else- where (3). For purposes of this experiment, those calves previously fed field- cured and field-baled alfalfa hay were designated group 1, those fed artificially- dried and ground alfalfa hay, group 2 and those fed artificially-dried and