

in such a program to improve the vitamin A potency of milk and 

 butter just as they have cooperated in the present survey. 



According to the figures in table 2, the average vitamin A po- 

 tency of the fat in the winter butter produced in the United States 

 was about 30 International Units per gram (1 pound of butter, or 

 454 grams, contains 80 percent fat) and that of the summer but- 

 ter was 49 International Units per gram. On this basis one may 

 calculate the average vitamin A potency of milk (4 percent fat 

 content) to be 1,140 International Units per quart for winter milk 

 and 1,800 for summer milk. Approximately 40 percent of the milk 

 consumed (as milk or milk products) by the people in the United 

 States is winter milk and 60 percent is summer milk. Thus, the 

 average vitamin A potency of the milk consumed annually is 

 1,530 International Units per quart. 



The "disappearance" of milk "for domestic consumption in all 

 forms" in the United States in 1941 was equivalent to 1.052 quarts 

 per capita per day. This amount of milk apparently furnished 

 1,600 International Units per capita per day for the total popula- 

 tion, or approximately one-third of the 5,000 International Units 

 of vitamin A recommended by the Food and Nutrition Board as 

 the daily allowance for a normal adult. 



This is a large contribution by the dairy industry to the national 

 need for vitamin A. But if, by proper feeding, the vitamin A 

 potency of winter milk were increased to that of summer milk, 

 that is, to 1,800 International Units per quart, the same amount 

 of milk that was consumed in 1941 would furnish about 1,894 

 International Units per capita per day, or nearly 40 percent of 

 the daily allowance for a normal adult. 



To what extent it may be possible to improve winter milk de- 

 pends on the results that may be obtained by investigators, farm- 

 ers, and others in improving the methods of conserving carotene 

 in hays and silages. Further improvement in summer milk is also 

 possible; the conditions which produce a lush pasture rich in 

 carotene also produce more feed and more milk, as well as better 

 milk. 



Pasture grasses and other roughages are the principal source of 

 the carotene used by dairy cows for the manufacture of vitamin A. 

 The farmer may waste much of the carotene produced by his 

 roughage crops or he may conserve it for human use if it is to his 

 advantage to do so. Of course, it is to his advantage to feed as 

 much carotene as his cows require for normal growth and health 

 and to bear normal calves. But if he were to try to produce winter 

 milk as rich in vitamin A as average summer milk, he would have 

 to feed his cows much more carotene than they would need 

 merely to maintain normal health or to bear normal calves. In- 



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