370 MISSOURI AGRICULTURAL EXP. STA V RESEARCH BULLETIN NO. IO 



Experiment No. 3. 



This feeding experiment was conducted with the same cow as 

 the preceding experiment and immediately followed that experiment. 



It seemed very probable that the reason the color of the milk 

 fat in Experiments i and 2 could not be lowered more than the uni- 

 form figure found in both experiments, i. e., about 8 units of yellow, 

 was due to the fact that the ration was supplying a small amount of 

 pigment and also to the fact that the normal storage, that in the 

 blood serum, had not been exhausted. It seemed reasonable to sup- 

 pose, therefore, that if the first factor was eliminated at the outset, 

 the second would necessarily also be eliminated if the experiment was 

 continued for a sufficient length of time. The experiment here re- 

 ported was for the purpose of testing the validity of this supposition, 

 and also for the purpose of ascertaining to how low a point the color 

 of the milk fat could be reduced. The ration chosen was one which 

 would supply the least amount of carotin and xanthophylls. It was 

 composed of cottonseed meal and cottonseed hulls. The results of 

 the experiment are given in Table 13. 



The supposition stated above was fully borne out by the long 

 continued feeding of a practically non-pigmented ration. At the end 

 of 52 days' feeding, the cow was producing absolutely colorless butter. 

 It was only when the rendered butter was viewed in the tintometer 

 that a very slight amount of color could be detected. This very 

 slight amount of color was due to the fact that the normal storage 

 of pigment in the body, that in the blood serum, had not been com- 

 pletely exhausted, as will be shown in a subsequent paper of this 

 series. It is probable also that the body was being drawn upon for 

 some of its pigments, for the animal suffered somewhat from under- 

 feeding on this ration. It is also possible that a very small amount 

 of carotin was being supplied by the oil in the cottonseed meal and 

 hulls. For practical purposes such a supply of pigment would of 

 course be considered absolutely negative. 



