IX. REQUIREMENTS AND FACTORS INFLUENCING THEM 571 



riMluiioinciit is J15 to J20 of the MFD lor adult Icnuik^ rals. llw luiiiinumi 

 amounts lor pivvcMition of musch^ dystrophy in nursiinji^ rats from E-low 

 mothers depends on the time when supplementation begins; the longer this 

 is delayed, as between the 10th and 17th day, the more is required.^ There 

 are no essential differences between the antisterility and dystrophy-pre- 

 venting potencies.'' As the daily dosage is reduced below 0.75 mg., the 

 length of the reproductive period is reduced.^ The gradual decline in pro- 

 ductivity of rat colonies may often be traced to the inadequacj^ of the vita- 

 min E supplies in commercial feeds. Such premature sterility appears to 

 have no effect on total span of life.^ For the rabbit the daily amount of a- 

 tocopherol to prevent and cure dystrophy has been given as 0.2 to 0.4 mg. 

 per kilogram ;'° the minimum need of the laying hen is 1.2 mg. per day" 

 and of the guinea pig 3 mg.^^ 



Like many other functions, that of vitamin E might be quantitatively 

 related to the 0.7 power of the body weight.'^ On this basis the daily require- 

 ment of an adult person of 70 kg. would be perhaps 30 mg. According to 

 surveys in Holland^^ and in the United States'^ the average individual in- 

 take of a-tocopherol is 6 mg. per 1000 cal. or less,^^ but the tocopherols of 

 vegetables are much less available than those in oils," and they may not 

 all be the a type. 



Few, if any, sufficiently controlled experiments have been made to es- 

 tablish the requirements of domestic animals that are known to need vita- 

 min E. Their natural food ordinarily supplies it in abundance, and the 

 preparation of a ration de\'oid of it, as by treatment with ferric chloride, 

 introduces other variables and may also fail of its purpose. 



The moot question has been whether domestic animals on their natural 

 feeds require supplements of vegetable oils or of tocopherol in order to jneld 

 the best returns in rate of growth and in reproduction. Sterility in cows 

 was reported to have been successfully treated with wheat germ oil,'^ the 



6 H. M. Evans and G. A. Emerson, Proc. Soc. Exptl. Biol. Med. 44, 636 (1940). 

 ' M. Goettsch and A. M. Pappenheimer, J. Nutrition 22, 463 (1941). 



8 H. M. Evans and G. A. Emerson, J. Nutrition 26, 555 (1943). 



9 C. M. McCay, G. Sperling, and L. L. Barnes, Arch. Biochem. 2, 469 (1943). 

 '0 S. H. Eppstein and S. Morgulis, J. Nutrition 22, 415 (1941). 



" M. Y. Dju, M. L. Quaife, and P. L. Harris, Am. J. Phi/.siol. 160, 259 (1950). 



'2 F. A. Farmer, B. C. Mutch, J. M. Bell, L. D. Woolsey, and E. W. Crampton, ./. 



Nutrition i2, 309 (1950). 

 13 P. L. Harris, Ann. N. Y. Acad. Sci. 52, 240 (1949). 

 '^ C. Engel, Ann. N. Y. Acad. Sci. 52, 292 (1949). 

 '5 L. E. Booher and I. T. Behan, ./. Nutrition 39, 495 (1949). 

 i« P. L. Harris, M. L. Quaife, and W. J. Swanson, ./. Nutrition 40, 367 (1950). 

 1^ C. Engel and J. T. ITeins, .Acta Brevia Neerl. Phi/siol. Pharmacol. Microbiol. 13, 



37 (1943). 

 's P. Vogt-.M0lk"r and F. Bay, Vet. J. 87, 165 (1931). 



