556 IX. CAROTENOIDS AND VITAMINS A 



milk occurs as the free alcohol. Parrish et aZ.^®" state that practically all 

 of the vitamin A in both the colostrum and the milk of the cow is in the es- 

 ter form. In goat's milk the proportion which is esterified amounts to 

 98%, according to Chanda.^^^ Goat's milk contained 60 T.U. of vitamin 

 A per gram of fat during the second week of lactation. The corresponding 

 figure for cow's milk was 49 I.U. This ratio persisted throughout lacta- 

 tion. The higher content in goat's milk may perhaps be related to the 

 greater activity of the thyroid gland in goats, which facilitates the absorp- 

 tion of carotene and its conversion to vitamin A, thus rendering more of 

 the vitamin available for secretion by the mammary gland. ^^^ 



a. The Carotenoids and Vitamin A in the Milk of Different Species. 

 Although carotenoids are generally considered to be typical constituents 

 of milk, there are a number of species in which only minute traces of these 

 chromogens occur. This is true of the goat,^^^'^^^ and of the Egyptian 

 buffalo.««2 



Elephant's milk contains only small amounts of vitamin A.^''^ The con- 

 tent is low in Indian buffalo milk, as well,^^'* although the butterfat con- 

 tains as much vitamin A as does that of the cow. The vitamin A content 

 of the butterfat from the Egyptian buffalo^^^ is twice that of cow butterfat. 

 Hvidsten and co-workers*^ ^ reported that carotenes are absent from the 

 colostrum of ewes. Therefore one would not expect the pigment to occur 

 in the milk of these species. No carotenoids are present in the milk of 

 aquatic mammals such as blue and fin-backed whales.''^'' Marked varia- 

 tions occur in the carotenoid content of the colostrum of different breeds of 

 cows. The highest figure has been reported for the colostrum of the Jersey 

 cow (347 Mg-/100 ml.)*^^ followed in turn by that of the Ayrshire breed (244 

 /ig./lOO ml.), 318 of "beef" cattle (129 /xg./lOO ml.),8«^ of Holsteui cows (59 

 to 236 Mg./lOO ml.866 and 100 jug-/100 m].),^^^ and of the Hariana and Sahiwal 

 breed (33.6 to 153.9 Mg-/100 ml.).^^^ According to Gillam et al.,^^^ colos- 

 tra from several breeds of cows contained the following concentrations of 

 carotene (expressed in mg. % fat): Friesan, 3.40; Ayrshire, 4.60; Guern- 



8" H. Hvidsten, L. G. Hansteen, and G. Broch, Meieriposten, 37, 148-153, 67-171 

 (1948). 



862 M. A. M. Abiil-Fadl, A. M. Ismail, and M. S. El Ridi, /. Roy. Egypt. Med. Assoc. 

 33, 521-526 (1950); Chem. Abst., 45, 278 (1951). 



8«3 Z. Markuze, Biochem. J., 33, 198-200 (1939). 



86" L. C. Dharmani and J. D. Chopra, Indian. J. Vet. Sci., 16, 158-166 (1946). 



865 R. W. Luecke, C. W. Duncan, and R. E. Ely, Arch. Biochein., 13, 277-282 (1947). 



866 R. G. Hansen, P. H. Phillips, and V. R. Smith, /. Dairy Sci., 29, 809-814 (1946). 



867 B. C. R. Sarkar, J. Dairy Sci., 31, 479-487 (1948). 



868 A. E. Gillam, I. M. Heilbron, W. S. Ferguson, and S. J. Watson, Biochem. J., SO, 

 1728-1734 (1936). 



