78 MANUAL OF MILK PRODUCTS 



ration. She lost weight regularly, and her milk production fell 

 off a great deal. It was apparent that the animal was drawing 

 heavily during this entire period from a storage of pigment in 

 her body. 



It may be stated that a slow lowering of the color of the milk- 

 fat, such as took place in this experiment, would be normal for 

 all Jersey cows whose ration is changed to an unpalatable, non- 

 pigmented one like that used in this experiment. The explana- 

 tion for this is found in the high color of the body fat of this 

 breed of cows. We therefore have here a clear explanation of 

 why Jersey cows will sometimes apparently give yellow milk- 

 fat during the winter months when their food is almost or 

 entirely lacking in carotin and xanthophylls. Under these 

 conditions if the body fat is called upon to supplement the diges- 

 tion products of the food in the production of milk-fat at the 

 same time the blood-serum storage of pigments is being drawn 

 upon, it is clear that the reduction in color of the milk-fat will 

 be very gradual, and a complete elimination of color may require 

 a long period of time. 



The foregoing experiments have shown conclusively that dairy 

 cows, exclusive of breed, are dependent on the carotin and 

 xanthophylls in their feed for the pigment of their milk-fat, in 

 other words, that they cannot produce the pigment which is 

 thus secreted. 



Relation between color of milk-fat and breed of cow (Palmer and 

 Eckles). 



The question is at once raised as to wherein lies the so-called 

 breed characteristic which is so much emphasized by the breeders 

 of Guernsey and Jersey cattle? It will not be denied that a 

 breed characteristic does exist in connection with the color of 

 butter-fat. We believe, however, that the data now to be pre- 

 sented will show that this breed characteristic has been over- 

 emphasized. 



Since the butter-fat is dependent upon the food of the cow for 



