POSSIBILITIES FOR IMPROVING THE VITAMIN A 

 POTENCY OF MILK AND BUTTER 



There is ample experimental evidence that 

 the vitamin A potency of milk, and also of the 

 butter made from, the milk, can be readily 

 changed by increasing or decreasing the quan- 

 tity of carotene in the cows' ration. The large 

 increases in the vitamin A potency of the sum- 

 mer butter over the winter butter produced in 

 the 14 States for which results are given in table 2 no doubt reflect 

 an increase in carotene consumption by the cows. when they were 

 put on pasture. 



The question as to whether or not there are conditions other 

 than the quantity of carotene in the feed that affect the efficiency 

 of its utilization by the cow has not been investigated adequately. 

 It is obvious, however, from the large amount of experimental 

 work in various laboratories, that any condition which tends to 

 increase the lushness of pastures or the carotene content of winter- 

 fed forages — either silages or hays — will increase the vitamin A 

 potency of milk and butter very greatly. Hays that are cured in 

 such a way that they retain their green color are rich in carotene, 

 whereas hays that have lost their green color in curing may be 

 very poor sources of carotene. Alfalfa hays may be rich sources of 

 carotene or they may be worthless in this respect; timothy hays 

 may vary manyfold in their carotene content. Silages made from 

 corn, hays, and other crops lose very little carotene during storage 

 if properly made and stored, but the carotene content of the silage 

 will depend on the carotene content of the crop at the time it was 

 harvested and ensiled. Most crops decrease rapidly in carotene 

 content as they mature or lose their green color. 



Much improvement in the vitamin A potency of the milk and 

 butter produced in this country could be brought about immedi- 

 ately if the present knowledge concerning suitable farming and 

 feeding methods were more widely put into practice. Improve- 

 ments in pasture management and the development of more prac- 

 tical and economical methods of producing, processing, and pre- 

 serving forages to increase the carotene content of the dairy ration 

 would contribute to further improvement in the vitamin A 

 potency of the milk and butter. Investigations along these lines 

 are now in progress in many States. Similar studies are being 

 conducted cooperatively by the Bureau of Dairy Industry and the 

 Bureau of Plant Industry, Soils, and Agricultural Engineering of 

 the United States Department of Agriculture. It has been recom- 

 mended that the State stations and Federal laboratories cooperate 



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