CAROTIN, THE PRINCIPAL YELLOW PIGMENT OF MILK FAT 399 



of the two cows was represented by the caul fat. The caul apron 

 of Cow 25 had a net weight of 12,132 grams; that of Cow 21 a net 

 weight of 7,364 grams. It is here that the great difference in color 

 is noticeable. In fact, if all the fat on the body of Cow 21 had 

 been rendered and its color compared with the same from Cow 25, 

 the difference in color would have been very marked. 



There can be no doubt that the above data is conclusive as to 

 the effect of feeding a non-pigmented ration to a fattening cow whose 

 fat had been largely eliminated by starvation previous to the feed- 

 ing of the colorless ration. In other words, it is apparent that the 

 body fat of the Jersey cow is colored primarily because the food is 

 rich in carotin and xanthophylls during the time the fat is on. The 

 blood serum of both cows contained carotin at the time of slaugh- 

 tering. Unfortunately no comparison was made of the amount in 

 the serum of the two cows. No doubt there was a much smaller 

 amount in the blood serum of Cow 21, than in the serum of Cow 25. In 

 both cows there was no known path of elimination of the blood pig- 

 ment during the starvation period, the cows being both dry and 

 barren. During the fattening period of Cow 25, the demands made 

 on the blood store by the body fat producing cells, was replenished 

 by the food. In the case of Cow 21, however, there was no replen- 

 ishing source, and the amount in the serum must have greatly 

 diminished. 



The data resulting from this experiment have some significance 

 aside from the relation of the body fat to the food of the cow. The 

 fact that the outside fats of the two cows were of equal color, and 

 the inside fats, especially the caul and rib plate fat, were of such 

 widely different colors, would seem to indicate what fats are drawn 

 upon first in starvation in this class of animals, and what fats are 

 laid on first during fattening. 



Relation Between Color of Body Fat and Breed of Cow. 



Considerable attention was given in connection with the study 

 of the milk fat pigment, to a study of the relation of the breed to 

 the amount of pigment in the fat. This study showed that the re- 

 lation of breed to milk fat coloration is a relative one, Holstein and 

 Ayrshire cows producing well-colored butter fat as well as Jerseys 

 and Guernseys under proper feeding conditions. It was also shown 

 that under certain conditions there was no difference in milk fat 

 coloration among the different breeds. These results naturally raised 

 the question whether a similar study of the body fat pigmentation 



