90 MANUAL OF MILK PRODUCTS 



of the milk-fat. This is emphasized in the case of Cow No. 301, 

 because the milk production in the two periods is known to have 

 been the same. If there is an influence upon the color of the 

 whey, it certainly is not nearly so pronounced as it is upon the 

 color of the milk-fat. Besides, this apparent result is of no 

 value whatever in explaining the wide difference between the color 

 of the whey of the different breeds, for when those readings 

 were taken all the cows were on the same ration, consisting of 

 alfalfa hay, corn silage, and a grain mixture of corn, bran, and 

 oil meal. 



It is to be concluded, then, that the feed has little or no influ- 

 ence upon the color of the milk whey. Certainly slight individ- 

 ual variations in the color of the whey are to be expected from 

 time to time, and it was probably merely accidental that the 

 color of the whey was somewhat lower in each case in the period 

 when the milk-fat was very low-colored, for there was a consider- 

 able lapse of time in both cases between periods 1 and 2. This 

 question was not considered of sufficient importance to pur- 

 sue further. 



These investigators sum up the results of their work as follows : 



Lactochrome, the yellow pigment of milk whey, is very closely 

 related in chemical and physical properties to urochrome, the 

 specific yellow pigment of normal urine, and is very probably 

 identical with it. 



The presence of lactochrome was found to be characteristic 

 of the milk of all breeds of cows tested, i.e. Ayrshire, Jersey, 

 Holstein, and Shorthorn. The amount of lactochrome appears 

 to be largely a breed characteristic, with the Ayrshire and 

 Jersey breeds ranking considerably above the Holstein and 

 Shorthorn. 



The presence of comparatively large amounts of lactochrome 

 in the milk of some animals is of considerable importance in 

 imparting to milk its characteristic yellow color. 



Lactochrome was found in sheep's milk, often in much larger 



