CAROTIN, THE PRINCIPAL YELLOW PIGMENT OF MILK FAT 409 



was found that Holstein cows may also possess high-colored body 

 fat. At least there seems to be more breed characteristic in this 

 respect, than in the case of the pigmentation of the milk fat. There 

 is no foundation, however, for the belief that beef has a lower value 

 because its fat has a high color. If this pigment is the same as is 

 demanded by the consumer for butter, why should not beef with high- 

 colored fat also be more desirable ? It is recognized of course that 

 some of the unfavorable attitude toward beef with highly colored 

 fat arises partially from the fact that it indicates that the beef prob- 

 ably came from a dairy cow. The two ideas are nevertheless very 

 closely associated. 



The normally high color of the body fat of Jersey cows and 

 also of those of the Guernsey breed, explains why cows of these breeds 

 often appear to be producing well-colored butter on a ration deficient 

 in carotin and xanthophylls. Several statements in regard to this 

 have already been made. This will bear repetition, however, because 

 the subject is an important one. Briefly, it may be said that when 

 cows whose body fat has a high yellow color are put upon a ration 

 deficient in carotin and xanthophylls and also, as is usually the case 

 with such rations, deficient in food value, the body fat is called upon 

 to furnish energy value for the animal and also in many cases to 

 supplement the food digestion products in the production of milk 

 fat. It is readily seen that in such cases an important source is 

 opened up for pigments for the milk fat. Just how important this 

 source could be would depend upon the amount of highly colored 

 body fat available for the needs of the body, and upon the rapidity 

 with which it would be used up. If our experimental data are cor- 

 rect showing that the inside fats, such as the caul fat and rib plate 

 fat, are the first drawn upon in starvation of this class of animals, 

 then the amount of available highly colored fat would be rather 

 large. Dairy cows usually have a fairly abundant amount of these 

 fats, especially the caul fat. It is thus readily seen that a continuous 

 drawing upon these inside fats for a long period of time would result 

 in a very slow and gradual reduction of the color of the milk fat. 

 The deduction that the animal was actually producing colored milk 

 fat on a carotin-xanthophyll-free ration would, therefore, be quite nat- 

 ural but nevertheless entirely false. 



In a similar manner it is readily seen why the breeders of Jer- 

 sey and Guernsey cattle have been led to believe that the yellow skin 

 secretions of these breeds are indicative of their ability to produce 

 yellow milk fat. It is interesting to find that the yellow pigments 

 of these secretions are carotin and xanthophylls. It should be clearly 



