424 MISSOURI AGRICULTURAL EXP. STA. RESEARCH BULLETIN NO. 12 



The above table shows in a very striking manner that the amount 

 of carotin in the blood serum of the lactating cow, as well as the 

 amount of carotin and xanthophylls in the milk fat, is dependent upon 

 the ration. The figures in the table also show very clearly why the 

 butter fat in the first two cases was not absolutely colorless. These 

 two samples were taken at the end of a long-continued feeding of 

 a ration almost entirely lacking in carotin and xanthophylls, which 

 was planned for the purpose of eliminating as far as possible the 

 color from the milk fat. It is evident that this was not accomplished 

 in the strictest sense of the word because the blood serum in both 

 cases still contained a small amount of carotin. 



The results of these studies were so striking that it was con- 

 sidered advisable to confirm them if possible with other animals. 

 We fortunately had at hand, 6 cows of 3 different breeds, all pure 

 bred animals, which were in ideal condition for such an experiment. 

 They had all just completed an experiment in which their feed for 

 12 to 14 weeks had been essentially a non-pigmented one, being made 

 up of cottonseed meal, corn stover and very light-colored timothy 

 hay. A night and morning milking of each cow was combined 

 and after determining the percentage of fat in the combined sample l 

 the milk was separated, the cream churned, and the color of the 

 rendered butter fat observed in the Tintometer. The same day, sam- 

 ples of blood were drawn from each animal and the color of the 

 serum determined by the method described above. The feed of the 

 cows was now changed so that it was largely made up of alfalfa 

 hay, rich in carotin and xanthophylls, and later a little fresh green 

 pasture grass. Thirty days after the cows had been on this feed 

 the first experiment was repeated and the color of the butter fat 

 and blood serum again observed. The results of this experiment 

 are given in Table No. 4. 



1. The weight of the combined sample was also recorded. 



