allowance (5,000 International Units) recommended for normal 

 adults by the Food and Nutrition Board of the National Research 

 Council. 



The effect of commercial storage and handling on the vitamin 

 A potency of butter was studied by seven of the State experiment 

 stations, and the results indicate that the effect of storage and 

 handling is negligible. 



Four State experiment stations investigated the vitamin A 

 potency of butter sold on retail markets in their respective areas 

 and found no significant difference between the average vitamin 

 A potency of the butter on the retail markets and the average of 

 the creamery butter produced in this country. 



Milk produced under winter-feeding conditions has an average 

 vitamin A potency of 1,140 International Units per quart (4 per- 

 cent fat basis) and that produced under average summer-feeding 

 conditions has a potency of 1,800. The average potency of the 

 total supply of milk which disappears annually for domestic 

 consumption is 1,530 International Units per quart. When the 

 disappearance of milk for domestic consumption in all forms 

 averages 1.052 quarts per capita per day, as it did in 1941, milk 

 and milk products furnish the total population of this country 

 about 1,600 International Units of vitamin A per capita per day, 

 or nearly one-third of the recommended allowance. 



The results of this study afford a practical demonstration of 

 the fact, previously established by many investigators, that the 

 vitamin A potency of milk and butter is dependent on the quan- 

 tity of carotene in the diet of the cow. Since much of the milk 

 now produced in summer has a vitamin A potency of from 2,500 

 to 3,000 International Units per quart and some of the butter has 

 well over 20,000 units per pound, it is apparent that much could 

 be done to improve the average potency of the annual output by 

 adopting better feeding practices in winter, and possibly in sum- 

 mer also. 



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PROCEDURES USED IN CONDUCTING THE SURVEY 



Method of Determining the Vitamin A Potency of Butter.— 



The vitamin A content of the butter was determined by using the 

 antimony trichloride method, taking into account the color given 

 by other materials in the butter which react with this reagent. 

 The procedure was a modification of the one used by Koehn and 

 Sherman in analyzing cod-liver oil. During the course of the sur- 

 vey numerous laboratories tested the method with butter to which 

 known quantities of crystalline vitamin A had been added and 

 found that only about 93 percent of the vitamin A was recovered 

 in the analysis. This loss of 7 percent was assumed to occur in 



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