VITAMINS 335 



the formation ol essential protoplasmic components and in the 

 metabolic conversion of purines and pyrimidines into compounds 

 suitable for excretion. Xanthine oxidase contains iron and molybde- 

 num with the FAD group, and all are essential for its action. 



During the metabolism of fats, various acyl coenzyme A oxidations 

 occur. These require flavoproteins which catalyze the removal of 

 hydrogen atoms from the a and f3 carbons of the acyl group. This 

 particular reaction 



O 



II 

 CH3(CH2)„CH2— CH2CSC0A + FAD • protein -^ 



acyl coenzyme A 



o 



II 



CH3(CH2)„CH=CHCSCoA + FADH2 • protein 



may play only a catabolic role by transferring electrons to the cyto- 

 chrome system by way of a "cytochrome reducing factor," also a flavo- 

 protein but not yet well characterized. A variety of other flavoproteins 

 participate in still other oxidations of importance, particularly of 

 amino acids. Specialized discussions may be consulted for details. 



Requirements 



Recommended daily allowances for optimal nutrition range from 

 1.5 to 3.0 mg., depending on age, sex, and physical activity. The high- 

 est allowance (3.0 mg.) is recommended for pregnant and lactating 

 women. 



Recommended allowances for domestic poultry are expressed in 

 terms of milligrams of riboflavin per pound of feed rather than on 

 the basis of daily intake. Starting chicks should receive feed containing 

 about 1.6 mg. of riboflavin per lb., and the allowances for laying 

 and breeding hens are 0.9 and 1.3 mg., respectively. A ration contain- 

 ing sufficient riboflavin for egg production may not be sufficiently rich 

 in this vitamin to ensure maximal hatchability. The supply of ribo- 

 flavin in the egg nuist be high enough to allow full development and 

 growth of the chick. Otherwise it dies of a deficiency before hatching. 



A mutant strain of White Leghorns is now available with a genetic 

 incapacity in the hens preventing transfer of sufficient riboflavin to 

 the egg for hatching. Fertilized eggs are otherwise normal, since 

 injection of riboflavin leads to hatching of chicks normal except for 

 their inherited tendency to lay eggs deficient in the vitamin. 



Turkeys appear to have a higher requirement than chickens. Poults 

 and breeders require, respectively, 2 and 1.6 mg. of riboflavin per lb. 

 of feed. 



