CAROTIN, THE PRINCIPAL YELLOW PIGMENT OF MILK FAT 385 



The results of these experiments are of considerable practical 

 importance. It is readily seen, for instance, that the peculiar popular 

 conception of the enhanced value of butter on account of a high 

 yellow color is absolutely without foundation. It is furthermore seen 

 that the prevailing opinion among some cattle breeders that Guernsey 

 and Jersey cows are able to synthetically produce a high colored but- 

 ter fat under all conditions is also unfounded. It has been shown 

 that all breeds of cows will produce well-colored butter fat under 

 proper feeding conditions. The reverse has been shown to be espe- 

 cially true, namely that a cow, regardless of breed, cannot produce 

 high colored butter fat under normal conditions, unless the food con- 

 tains the pigments which are utilized for that purpose. 



With our present knowledge, however, we would not be justified 

 in saying that there is no breed characteristic in connection with the 

 color of butter fat. Under apparently equal conditions Jersey and 

 Guernsey cows usually give higher colored milk fat than Holstein or 

 Ayrshire cows. We have been able to offer some evidence, however, 

 showing that during a moderate pigmentation of the milk fat, this 

 difference largely disappears when the amount of fat produced and 

 the proportion of the ration which is the source of the pigment are 

 taken into consideration. Further experiments would be required to 

 ascertain whether this is true under all conditions of milk fat pig- 

 mentation or only true for moderate pigmentation. The data already 

 at hand at least entirely justify the statement that the so-called breed 

 characteristic has been given more emphasis than is warranted by an 

 actual study of the facts. 



The results of our experiments are furthermore of considerable 

 physiological significance. A direct source for the lipochromes of the 

 cow has been established, which opens the question of a similar 

 source for all animal lipochromes. The lipochrome of milk fat has 

 been increased or decreased with great ease by merely varying the 

 food of the cow. Such a result throws great doubt upon any physio- 

 logical significance which the lipochromes have been supposed to exert 

 in the animals in which they have been found. Apparently it is merely 

 a question of the inability of the animal body to throw off the excess 

 of carotin and xanthophylls contained in its food. Experiments will 

 reported in a later paper of this series showing that the blood serum, 

 of the cow at least, very rapidly takes up the carotin (especially) of 

 the food and carries it through the body in combination with an albu- 

 min of the serum. 



