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Utilization by the Chick of Vitamin A from Different Sources

I. Crystalline Carotene, Crystalline Vitamin A Acetate, and "Black Cod" Liver Oil¹

Departments of Agricultural and Biological Chemistry and Poultry Husbandry, The Pennsylvania State College, State College

The comparative utilization by Barred Plymouth Rock chicks of vitamin A from crystalline carotene, crystalline vitamin A acetate and "Black Cod" liver oil was studied in two experiments carrying the birds to 8 weeks of age. Efficiency of utilization was judged by gain in body weight and by liver storage of vitamin A. The concentration of vitamin A in blood plasma was also studied with a view to determining possible relationships which may exist between blood content and liver stores of vitamin A. The results of these studies permit the following conclusions:

1. When sufficient vitamin A was ingested to raise the concentration in the blood to a certain level, crystalline carotene, crystalline vitamin A acetate and "Black Cod" liver oil were equally effective in sustaining a satisfactory rate of growth.

2. For the sources employed, the minimum amount of vitamin A required for satisfactory growth of the chick to 8 weeks of age was between 500 and 1,000 I.U. of vitamin A per pound of diet.

3. Excessively high vitamin A intake exerted a growth-depressing effect.

4. The amount of vitamin A present in the blood was related to the vitamin A intake.

5. A value of approximately 50 I.U. of vitamin A per 100 ml of blood plasma was observed to be critical for liver storage of the vitamin, in that the last measurable reserves of vitamin A in the liver were drawn upon to maintain the plasma value at this level.

6. A value of approximately 100 I.U. of vitamin A per 100 ml of blood plasma was apparently necessary to permit storage of vitamin A in the liver when supplementation followed vitamin A depletion.

7. The blood plasma level of vitamin A tended to remain relatively static at the expense of liver storage of the vitamin.

8. A high storage of vitamin A in the liver was not essential for satisfactory growth, provided sufficient vitamin A was supplied in the daily diet.

9. Of the sources employed, crystalline vitamin A acetate was most effective and crystalline carotene least effective in promoting concentration of the vitamin in the blood plasma and in the liver.

Manuscript received 24 March 1951.