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Colostrum Milk and its Vitamin A Content

Department of Biochemistry, College of Agriculture, University of Wisconsin, Madison

ABSTRACT

A study of the vitamin A concentration of colostral milk has been made. The vitamin A content of the colostrum from barn-fed heifers in the first lactation was found to be more than double the vitamin A content of the colostrum from the same cows in the second lactation. A seven-fold variation in colostral vitamin A potency occurred in these cows which had been fed identical rations and maintained under uniform conditions.

A marked increase in the blood plasma vitamin A concentration of the newborn calf followed the ingestion of colostrum and tended to reflect the concentrations of vitamin A present in the colostrum of their dams.

With cows isolated from their calves the vitamin A potency of their colostrum of the first and second milkings was about the same. However, cows which were allowed to remain with their calves and in addition were milked out twice daily showed a decided drop in vitamin A potency between the first and second milking. The intravenous injection of 10 I.U. of oxytocin at the time of milking in cows isolated from their calves also produced a similar drop in vitamin A potency between the first and the second milking.

The chief drop in concentration of vitamin A in the change from colostrum to normal milk occurred during the first three milkings following parturition, thereafter there was a gradual drop in vitamin A concentration over a period of several days to the concentration found in milk produced in mid-lactation.