686 VII. VITAMINS A 



can be markedly increased by feeding massive doses of vitamin A to the 

 cows-i^^'i"* These results are illustrated in Table 6. 



TABLE 6 

 Effect of Supplementary Vitamin A on the Composition of Milk Fat of Cows 



Daily Length Carotene and vitamin A/g. fat 



vitamin A of 



supplement, supplement, /3-Carotene, Vitamin A, Total vit. A, 



I.U. weeks iig. I.U. I.U. 



Holstein 



Guernsej^ 



9.79 25.5 41.8 



2,650,000 3 4,99 223.2 231.5 



5,300,000 11 2.28 178.4 182.2 



TABLE 7 

 Carotene and Vitamin A in Colostrum from Various Breeds of Cattle" 



(The first sample in each case represents the colostrum; the second sample is the mature 



milk) 



" I. M. Heilbron, W. E. Jones, and A. L. Bacharach, Vitamins and Hormones, 2, 155- 

 213 (1944), p. 195. Data from A. E. Gillam, I. M. Heilbron, W. S. Ferguson, and S. J. 

 Watson, Biochem. J., SO, 1728-1734 (1936), p. 1733. 



One interesting relationship A\hich is unexplained is the suppressing ac- 

 tion of oral doses of vitamin A on the level of milk carotene. The effect 

 develops slowly and continues for a number of weeks after the vitamin A 



'0^ H. J. Deuel, Jr., N. Halliday, L. F. Hallman, C. Johnston, and A. J. Miller, J- 

 Nutrition, 22, 303-313 (1941). 



105 H. J. Deuel, Jr., L. F. Hallman, C. Johnston, and F. Mattson, /. Nutrition, 23, 

 567-579(1942). 



