514 IX. CAROTENOIDS AND VITAMINS A 



carotene occurs in the iris of cattle.*'-- The amount of carotene in the 

 Uver of cows was found by Ka**" to vary with the seasonal intake of carot- 

 enoids. In the tests of Ganguly et a/.,'-^^ the average value for liver caro- 

 tene was 20.6 Mg-/g-) with a range between 12.0 and 32.6 Aig-/g-, while the 

 mean xanthophyll value was 1.2 Mg./g., with a range between 0.8 and 1.3 



/^g-/g- 



Preformed vitamin A is likewise present in the blood and liver of cows. 

 Moore^^^ recorded an average figure of 150 I.U./g. liver for cows which pre- 

 sumably had received large amounts of carotene in the form of grass over 

 long periods. Moore and Payne*" cited a value of 144 I.U./g. for beef 

 . liver and of only 39 I.U./g. for calf liver. 



c'. Horses: Zechmeister and Tuzson*^ reported that (5-carotene is the 

 predominant carotenoid deposited in the fat of horses; this confirms the 

 early work of Palmer,-*^ who showed that the same situation obtains in the 

 blood. It is also suggested that, in horses as in cattle, the preponderance of 

 the carotenes in the liver and other tissues, and the low levels of the xantho- 

 phylls in these tissues, may be ascribed to selective absorption, since rela- 

 tively larger amounts of xanthophylls, as compared with carotene, were 

 found in horse dung after the feeding of green fodder.*^'*^- Palmer and 

 Eckles-''*'^^^ suggested that the absence of xanthophylls from the body carot- 

 enoids might be due to their destruction in the gastrointestinal tract. 



In addition to the carotenoids, vitamin A is also a component of the blood 

 and liver of horses. Rudra^*'- reported an average vitamin A level in the 

 livers of English horses of 628 I.U./g., with variations between 32 and 2000 

 I.U./g. This compares with a figui*e of 1173 I.U./g. for horse hver re- 

 ported by Andersen and Hart,*^^ and one of 500 I.U./g recorded by Jensen 

 and With.'''^ Andersen and Hart*'*^ found that the vitamin A in the liver 

 of the horse was reduced to zero when the animals were maintained on a 

 vitamin A-free diet for 152 days. 



d'. Sheep: According to Peirce,-*^ the livers of Australian sheep contain 

 only traces of carotene (1 to 3 /ig./g.). The amount of the carotene was 

 not influenced by a diet which completely depleted the liver of vitamin A. 

 The vitamin A content of normal sheep liver was reported as 459 I.U./g., by 

 Moore and Payiie.*" The vitamin A level remained uniform in winter 

 and summer, in contrast to the values in the livers of cattle and pigs, which 

 were higher in the summer. 



e'. Miscellaneous Animals Which Do Not Accumulate Carotenoids: 



6« H. Ka, Re'pt. Inst. Sci. Research, Manchoukuo, 3, 371-385, tra«s. 2 pp. (1939). 



6" T. Moore and J. E. Payne, Biochem. J., 36, 34-36 (1942). 



"2 L. Zechmeister, P. Tuzson, and E. Ernst, Nature, 135, 1039 (1935). 



«" A. C. Andersen and G. H. Hart, Am. J. Vet. Research, 4, 307-317 (1943). 



