FACTORS AFFECTING THE REQUIREMENT 801 



side appears to decrease biopoteiicy, whereas increased uusaturation on the 

 carboxyl side may potentiate it. 



5. Factors Affecting the Requirement for Essential Fatty Acids 

 (/) The Effect of Species 



Although the disco\'ery of the requirement for EFA as a dietary constit- 

 uent was first made on the rat, and considerable information has been 

 obtained by the study of this species, the requirement for these acids has 

 been found to be very widespread. FraenkeJ and Blewett^"^ demonstrated 

 that the EFA are required by certain insects, such as the Mediterranean 

 flour moth (Ephestia kuehniella), the tobacco moth {E. eluieUa), the fig 

 moth (E. cautella), and the Indian-meal moth {Plodia mierpunctella I^ep.). 

 This is also true of the pink boll-worm (Pectinophora gossypiella Saund.) 

 studied by Reiser, Kerur, and Vanderzant.^"^ 



According to White and associates, ^°^ mice develop a deficiency similar 

 to that of rats on regimens devoid of EFA. In fact, this species has re- 

 cently been used by Decker et oZ.^^" for a comprehensive study of EFA. 

 Although Russell and co-workers^^^ were unable to provoke a fat deficiency 

 in chickens, Reiser^^^ was later successful in producing the deficiency in this 

 species. In the latter tests, sucrose was used in the diet in place of the 

 ground yellow corn employed by Russell et aZ."^ It was suggested that, 

 in the earlier tests, there was a sufficient supply of EFA, chemically 

 combined with the starch particles and not removed by the usual methods 

 of extraction, to prevent EFA deficiency. 



The hog represents a species relatively refractory to EFA deficiency. 

 The failure toinduce a fat deficiency in this species may be related to the 

 high content of EFA frequently stored in its tissues. Thus, Ellis and Isbell 

 113,114 looted that lard from hogs on a high-soybean diet sometimes had a 

 linoleate content as high as 31 .9%. Ellis and Zeller^^^ found that, when the 

 animals were subjected to a fat-free diet, the linoleate content decreased 

 to as little as 1.3%. It would appear that fat deficiency has not been 



lo'G. Fraenkel and M. Blewett, J. Exptl. Biol, 22, 172-190 (1946). 

 1"* R. Reiser, D. R. Kerur, and E. S. Vanderzant, unpublished data, 1955. 

 108 E. A. AMiite, J. R. Foy, and L. R. Cerecedo, Proc. Soc. Exptl. Biol. Med., 54, 301- 

 .302(194.3). 



I'o A. B. Decker, D. L. Fillerup, and J. F. Mead, ./. Nutrition, 41, 507-521 (1950). 



1" W. C. Russell, M. W. Tavlor, and L. J. Polskin, ./. Nutrition, 19, 555-502 (1940). 



"2 R. Reiser, /. Nutrition, 42, 319-323 (1950). 



"3 N. R. Ellis and H. S. Isbell, J. Biol. Chem., 69, 219-238 (1926). 



'1* X. R. Ellis and H. S. Isbell, /. Biol. Chem., 69, 239-248 (1926). 



"5 N. R. Ellis and J. H. Zeller, ./. Biol. Chem., 80, 185-197 (1930). 



