384 MISSOURI AGRICULTURAL EXP. STA., RESEARCH BULLETIN NO. IO 



that when fifteen grams per day of Sudan III dissolved in oil was 

 fed to a cow for three successive days, there was no indication of 

 the dye in the milk. On the other hand, in the feeding experiments 

 with Cow No. 301 where the bleached alfalfa hay was changed to 

 timothy hay containing a small amount of carotin, there was also 

 apparently no effect on the color of the milk fat. 



It is especially noteworthy that all of the above feeding experi- 

 ments which involved yellow corn are united in pointing to its inabil- 

 ity to impart any color to the butter fat. This result is not so sur- 

 prising, however, when viewed in the light of the character of the 

 pigment of yellow corn as shown in the chemical studies. It was 

 found there that the pigment is largely a xanthophyll. It may be 

 stated that the butter fat of Cow No. 301 during the last yellow corn 

 experiment failed to show the presence of the corn xanthophyll, when 

 subjected to careful examination. 



The feeding of carotin in the form of carrots to a cow giving as 

 low colored milk fat as Cow No. 301 gave an excellent opportunity to 

 study the proportion of carotin and xanthophyll in the resulting well- 

 colored butter fat. This investigation was reported in connection 

 with the study of the proportion of carotin and xanthophyll in butter 

 fat under varying conditions of production. It was found that the 

 xanthophylls were practically absent from the fat. The conclusion 

 is that the xanthophylls must be present in the food in large excess, 

 as in grass, before they will appear in the butter fat. 



It was mentioned above, and the fact is worthy of special notice, 

 that when the carotin and xanthophylls are withdrawn from the food 

 the falling off in color of the butter fat is sometimes very slow. In the 

 case of Jersey cow No. 57, it required twenty-seven days for the butter 

 fat to drop in color from 43 to 8.5 units of yellow. Normally, it should 

 require much less time for the color to drop this amount. For instance 

 it required only 12 days for a similar drop to be brought about in the 

 color of the milk fat of Jersey cow No. 59. In explanation of this 

 difference it may be stated that upon a normal plane of nutrition, the 

 blood serum furnishes the pigment for the milk fat. When the plane 

 of nutrition is below normal in a lactating cow the body fat is drawn 

 upon to aid in the production of milk fat and also for other purposes. 

 If the body fat thus utilized has a high yellow color, as is usually 

 the case in Jersey and Guernsey cows, the normal storage of pigment 

 for the milk fat will be continually, at least partially, replenished. 

 The reduction in color of the milk fat will then be much slower than 

 normal. It was stated above and will bear repetition, that we have 

 here an explanation of why Jersey cows apparently often produce high 

 colored milk fat on a low pigmented ration, as during the winter months. 



