Changes in the Level of Vitamin A and Carotene in the Blood Plasma of Dairy Cows Associated with Parturition and Beginning Lactation

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Abstract
The changes in blood-plasma vitamin A and carotene associated with parturition and beginning lactation were studied in 28 dairy cows. The total output of vitamin A and carotene in the colostrum during the first 3 days of lactation in 26 of these cows was also detd. Both vitamin A and carotene were found to decrease markedly in the blood plasma at the time of parturition and beginning lactation. Under the conditions of this expt. the max. decrease in blood-plasma carotene was reached one week following parturition and amounted to 46% of the 3-week pre-par-tum level. The max. decrease in blood-plasma vitamin A for the entire group was reached 3 days following parturition and amounted to 52% of the pre-partum level. The total output of vitamin A and carotene in the colostrum during the first 3 days post-partum averaged 48,847 [gamma] of vitamin A and 56,524 [gamma] of carotene.