Carotene and Vitamin A in Cattle Blood Plasma with Observations on Reproductive Performance at Restricted Levels of Carotene Intake

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Abstract
A method is described for the spectrophotometric determination of carotene and vitamin A in cattle blood plasma. The method is quite satisfactory for the determination of carotene but vitamin A values must be considered relative because of substances in the plasma extract which cause some interfering absorption. Vitamin A deficiency in cattle or an inadequate intake of carotene resulting in depletion of the animal's reserve can be detected by blood carotene and vitamin A analysis. The carotene and vitamin A content of blood plasma are dependent on the carotene intake and previous storage of these factors. After cattle have been depleted of carotene reserves, the blood carotene level is dependent on the carotene intake although there is some individual variation. The vitamin A content of blood plasma is closely related to its carotene content. However, vitamin A values tend to reach a stable level and do not increase proportionally with increasing carotene intake. Apparently normal calves were born in two cases to beef heifers that received 60 μg. of carotene from high quality dehydrated alfalfa leaf meal per kilogram of body weight previous to and throughout the gestation period. However, one of the calves gave signs of being deficient at about 1 month of age. Heifers receiving 30 and 45 μg. of carotene produced deficient calves although the cows themselves remained apparently normal. Blood plasma carotene and vitamin A values are given for a wide range of carotene intake and for seven heifers which gave birth to deficient or normal calves during the experiment.