192 CAROTINOIDS AND RELATED PIGMENTS 



The experiments demonstrated conclusively that the carotin content 

 of the cow's tissues as well as that secreted in the milk fat is deter- 

 mined by the carotin content of the ration. One of the interesting 

 features of the experiments was the demonstration that this relation 

 is independent of the breed of the cow; just as striking changes in 

 the pigmentation of the milk fat, blood serum and adipose tissue were 

 brought about in the highly colored breeds as in those which are not 

 usually so highly pigmented. So far as the blood serum is concerned 

 the breed appears to have no bearing on the maximum carotin con- 

 tent, as the data in Table 14 show. This fact, together with a certain 

 lack of parallelism between the changes in the carotin content of the 

 blood and corresponding changes in the carotin content of the milk 

 fat indicates that the breed differences involving the color of the milk 

 fat and adipose tissue are determined at the site of the synthesis of 

 the milk fat and adipose tissue. It is not at all improbable that the 

 carotin-albumin complex which carries the carotin in the blood serum 

 plays a prominent part in controlling these differences. 



A surprising feature of the experiments was the failure of a 

 xanthophyll-rich cattle food, such as yellow maize, to exert any appre- 

 ciable influence on the color of butter fat. This is brought out clearly 

 in Table 14. In the experiment reported in that table the ration con- 

 tained 6 pounds of yellow maize daily. In other experiments re- 

 ported by Palmer and Eckles (1914a) as much as 12 pounds of yellow 

 maize was fed without effect. These results are contrary to popular 

 opinion (compare Newbigin, quoted above), but are unquestionably 

 explained by the fact that carotin is only a minor fraction of the 

 pigment of yellow maize, the major pigment being xanthophyll, which 

 appears to play very little part in coloring the tissues or fluids of 

 dairy cattle. 



A word should perhaps be said regarding the experiment whose 

 results are summarized in Table 15. It is obvious on inspecting these 

 data that only certain parts of the body were affected. This is ex- 

 plained by the fact that the preliminary starvation period of the 

 animals failed to remove appreciable amounts of fats from the out- 

 side of the body or from around some of the vital organs. It seems 

 evident that the mesentery and related fats were drawn upon chiefly 

 during the period of partial starvation because it was the fat deposited 

 in these parts during the fattening period that was affected by the 

 carotinoid-deficient ration. 



Palmer (1915) carried out similar .experiments with fowls. The 



