• 1 April 1947
Abstract
A herd of purebred Brown Swiss dairy cows divided into 4 comparable groups has been studied for a period of 20 months. Three groups received daily supplements of: (1) 250,000 units of vitamin A, (2) 1.0 gm of mixed natural tocopherols, and (3) both vitamin A and tocopherols, and a fourth group received no supplement. Milk production, fat concentration in the milk, total fat production, and output of vitamin A and carotene in the milk were studied extensively. Shorter experiments were conducted on the tocopherol content of the blood and milk of the cows. Tocopherol supplementation increased milk-fat concentration about 27% and total milk production (“4% milk”) about 21%. The same response was induced in Guernsey cows fed vitamin E. Only cows in the same stage of lactation and as nearly matched as possible in other respects, such as age and number of lactations, were compared. Supplementation with vitamins A and E was no better than with vitamin A alone in increasing the vitamin A per se in the milk. However, the decrease in carotene concentration in the milk due to the feeding of vitamin A was less severe (approximately 23% below the control level rather than 33%) with the simultaneous administration of vitamin E. The efficiency of transfer of ingested vitamin A and carotene into vitamin A and carotene in the milk was not increased by supplementation with vitamin E alone. The average value for a 1-year period was 2.4%. This varied from about 6% in the winter under barn-feeding conditions to less than 1% in the summer when fresh pasture was available. The total output of vitamin A potency (vitamin A plus carotene) of the control cows varied from a maximum value in August to 30% of this in January. Carotene contributed about 34% of the total vitamin A activity of the milk, and this varied from 25% in winter to about 40% in summer. General improvement in appearance, reproduction, and health was noticed in the parts of the herd supplemented with vitamin E and vitamins A and E. Finally, in comparing the benefits to be derived from the 3 types of supplementation, E, A, and E + A, it must be concluded that the major benefit in health and milk output was derived from vitamin E alone. The only obvious result of vitamin A supplementation was to increase the vitamin A content of the milk, this at the partial expense of carotene content. The combined supplementation of E and A allowed the A content of the milk to rise without a pronounced fall of carotene, but the increase in butterfat which we have come to expect from vitamin E supplementation was entirely repressed by the vitamin A. Vitamin E therefore emerges as the preferred supplement to the ordinary diet of dairy cows.

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