VITAMINS 331 



supply the animals' needs. Minimal requirements for other species 

 cannot be set accurately because the values are known to vary with in- 

 dividual body weight, caloric intake, composition of the diet, and un- 

 known factors. 



As a result the dietary intakes usually recommended allow safety 

 factors and provide enough thiamine to prevent the appearance of 

 deficiency symptoms in normal individuals. For healthy human be- 

 ings the daily allowance is put at 0.5 mg. of thiamine per 1,000 cal. 

 consumed. On this basis, the total intake should range from 0.8 to 0.5 

 mg. for infants and to about 2.0 mg. for very acti\e iiulividuals of 

 larger-than-average size. 



Although birds are very susceptible to a lack of thiamine in the 

 diet, the poultry farmer is not required to give much thought to the 

 thiamine content of his poultry rations. Good poultry rations usually 

 contain more thiamine than the birds require. Starting chicks, up to 8 

 weeks of age, should receive about 0.9 mg. of thiamine per lb. of feed. 

 No requirements or allowances have been established for older birds. 



The daily allowances recommended for swine range from 1.4 mg. 

 of thiamine for pigs weighing 50 lb. to 4.2 mg. for hogs of 250 lb. 

 Lactating sows and breeding swine should receive about 6.3 mg./day. 



Thiamine is quite widely distributed in foods and feed stuffs, but 

 very few of our common foods are rich sources of this vitamin. The 

 richest natural sources are yeast, cereal grains, and pork. Potatoes and 

 other vegetables play an important role as a source of thiamine in 

 spite of the fact that these foods are not rich in this factor. White 

 floin-, like polished rice, is a poor source of thiamine because most 

 of the vitamin is lost in the refining process. Wheat bran is a fairly 

 rich source of vitamin Bj. Raw milk is not a good source of thiamine, 

 and the normal content may be reduced appreciably by pasteurization. 

 Yet milk is important in America as a thiamine source because of the 

 great volumes consumed. The outer layers of most seeds and most 

 animal tissues are rather high in thiamine and play important roles 

 in balanced diets. 



It is now customary to enrich white bread to replace the vitamin 

 lost in milling white flour. This extra supply supplements diets that 

 nutritional surveys show are marginal even in this country and Europe. 

 Nevertheless, cases of vitamin P>, deficiency are rare in the United 

 Slates except in chronic alcoholism, where it is sometimes correlated 

 with improper eating habits or lack of sufficient food. In the Far 

 East, use of polished rice as the dietary staple leads to great numbers 

 of cases of beriberi. Educational programs have improved the situa- 

 tion, but thousands of cases undoubtedly still occur in remote areas. 



