4IO MISSOURI AGRICULTURAL EXP. STA., RESEARCH BULLETIN NO. II 



borne in mind, however, that the only indication that a cow will secrete 

 yellow milk fat is that the food contains an abundance of carotin and 

 xanthophylls. 



SUMMARY. 



1. The yellow lipochrome of the body fat, corpus luteum and 

 skin secretions of the cow, like the lipochrome of butter fat, is com- 

 posed principally of a pigment whose physical and chemical properties 

 are identical with the carotin of green plants. The same pigment may 

 have associated with it one or more minor constituents whose physi- 

 cal and chemical properties are identical with the xanthophylls of 

 green plants. 



2. The carotin and xanthophyll pigments of the body fat are 

 derived from the food of the cow. The body fat of Jersey cows 

 formed on a ration deficient in carotin and xanthophylls, is devoid 

 of color. 



3. The body fat of Jersey and Guernsey cows is usually char- 

 acterized by a higher yellow color than cows of other breeds. This 

 is of great importance in explaining why cows of these breeds may 

 sometimes show a much slower elimination of the pigment from 

 milk fat on a non-pigmented ration, as during the winter months. 

 In these cases the body fat furnishes a supplementary source of pig- 

 ments for the milk fat. 



4. The yellow body fat of Jersey and Guernsey cows should 

 not be a point against the use of these animals for beef. The pig- 

 ments here are the same as those for which the consumer will pay a 

 higher price when present in butter. 



5. The breeders of Jersey and Guernsey cattle are probably 

 correct in their belief that the yellow skin and skin secretions of 

 these animals are characteristic of the breeds. It is not correct, how- 

 ever, that this characteristic is indicative of the ability of these ani- 

 mals to secrete yellow milk fat under all conditions. The only indi- 

 cation of this is whether the food contains an abundance of carotin 

 and xanthophylls. 



6. The blood serum of the new-born Jersey calf is free from 

 carotin and xanthophylls. The small amount of fat on the body is 

 tinted very faintly with these pigments. 



