CAROTIN, THE PRINCIPAL YELLOW PIGMENT OF MILK FAT 381 



plentiful supply of green alfalfa hay and some fresh green grass. 

 The data bring out two points worthy of emphasis. One of these 

 is that it is possible to find pure bred Holstein cows entirely lacking 

 in the so-called breed characteristic of color production. Holstein 

 Cow No. 213 for instance produced as much color in her fat in both 

 periods as any of the Jerseys. The low color of the milk fat of cows 

 No. 220 and No. 303 in the second period can only be explained at 

 present on the ground that it was due to some inherent characteristic 

 of the animals, which for lack of a better term may be called breed 

 characteristic. The other point brought out by the data is merely in 

 emphasis of the results obtained in the feeding experiments showing 

 that all breeds of cows suffer alike in regard to the color of their 

 milk fat when the pigments carotin and xanthophylls are withdrawn 

 from their food. At this time there is no breed characteristic. 



Not only does the breed characteristic disappear when the source 

 of the pigment is withdrawn, but it also disappears for all cows at the 

 time of maximum color in the fat, i. e. immediately after parturition. 

 Data was given in Table 8 showing the high color of the colostrum 

 milk fat for cows of three breeds. There was certainly no breed 

 characteristic evident there. 



There is one other breed difference yet to be considered, which 

 has led, probably more than anything else, to the belief that Jersey 

 and Guernsey cows can produce yellow butter fat at any time, regard- 

 less of feed. This difference has to do primarily with the storage of 

 pigment in the body, and its discussion belongs properly to the two 

 subsequent papers of this series. A brief statement here in regard 

 to it however will prevent a doubt arising in the minds of some read- 

 ers, whose practical experience is apparently contrary to the experi- 

 mental evidence here offered. 



Stating the question in hypothetical form, it may be said that 

 if a Jersey (or Guernsey) and a Holstein cow, both giving well-colored 

 milk fat, the possibility of which cannot be denied in the light of the 

 evidence which has been offered on this point, are put upon dry feed 

 containing little or no carotin and xanthophylls, the color of the milk 

 fat will drop much faster with the Holstein cow than with the Jer- 

 sey (or Guernsey) cow, unless great care is taken to provide a ration 

 as nourishing and palatable as the previous pigmented one. The re- 

 sult will be that the Jersey (or Guernsey) cow will appear to be pro- 

 ducing colored milk fat on a non-pigmented ration. The explanation 

 for this has already been given in connection with feeding Experi- 

 ments Nos. i and 6, and lies in the fact that the body fat of Jersey 

 and Guernsey cows furnishes a supplementary storage of pigments 



