558 IX. CAROTENOIDS AND VITAMINS A 



differences between the level in the colostrum and in milk. Thus, average 

 carotenoid values recorded for human colostra by different investigators 

 are 51 Mg-/100 m].,^^' and 25 to 34 jug./lOO ml.^so 



In general, the values (in /ig./lOO ml.) for human milk are considerably 

 lower,88i for example, 15f'^ 2 to 17;'''- 24 to 25;«^i and 17 to GO.^^^ jjru- 

 betz et al.^'^^ reported values for vitamin A in human milk ranging between 

 331 and 170 I.U. per 100 ml. (100 to 51 Mg-/100 ml.) at varying times dur- 

 ing the progression of the lactation cycle. Macy,^^^ likewise, carried out 

 extensive investigations on the proportion of vitamin A and of carotenoids 

 in human milk during various periods of lactation, and found higher values 

 for both carotenoids and vitamin A in colostrum than in milk. 



The colostrum of swine has been reported to have a carotenoid content 

 of 24 Mg-/100 ml.,^^^ while that of the goat is given as 12 to 46 ^ug./lOO 

 ml.^^^ Only traces of carotenoids appear in the mature milk of the latter 

 two species. Swine colostrum was found to contain 60 /xg. of vitamin 

 A/100ml.^«'^ 



b. The Effect of the Lactation Cycle on the Carotenoids and Vitamin A in 

 Milk. It has been shown in the previous section that a marked variation 

 obtains between the composition of the colostrum and that of the milk. 

 Colostrum is more concentrated and contains a larger proportion of practi- 

 cally every solid component, including carotene and vitamin A, than do the 

 milks produced subsequently. 



Chanda^^^ reported that, in cow's milk, vitamin A decreased gradually 

 up to the thirtieth week of lactation. Thereafter, when the yield of milk was 

 decreasing rapidly, both the per cent of fat in the milk and the per cent of 

 vitamin A in the fat showed small but definite increases. No change oc- 

 curred in the content of carotenoids as the lactation cycle progressed. 

 The vitamin A of milks during the second week of lactation amounted to 

 60 I.U./g. fat in goat's milk, while the content in cow's milk was 49 I.U./g. 

 fat. In the case of the goat, minimum vitamin A levels were reached dur- 

 ing the twentieth week of lactation. 



In the case of swine, Heidebrecht and co-workers*^^ reported the follow- 

 ing cyclic changes in the vitamin A in the milk (expressed in )ug./100 ml.) : 

 colostrum, 132; fifth day, 33; fifteenth day, 22; fifty-fifth day, 19. Swine 



880 L. Skurnik and M. Hellen, Z. Vitaminforsch., 15, 52-68 (1944). 



881 W. J. Dann, Bior.hem. J., SO, 1644-1651 (1936). 



882 C. Friderichsen and T. K. With, Ann. Paediat., 153, 11.3-143 (1939). 



883 I. G. Macy, Am. J. Diseases Children, 78, 589-603 (1949). 



884 R. Chanda and E. C. Owen, Biochem. J., 51, iv (1952). 



886 A. A. Heidebrecht, R. Mac Vicar, O. B. Ross, and C. K. Whitehair, /. Nutrition, 

 U, 43-50(1951). 



