356 FEEDS AND FEEDING 



rarely happens when green feed is supplied. He writes that reducing the 

 grain ration and giving 2 or 3 doses of Epsom salts may remove the 

 trouble. 



The whole subject of odors and flavors in milk and dairy products is 

 greatly complicated by the fact that there is a wide range in the ability 

 of different individuals to detect and distinguish them. Flavors and 

 odors plainly evident to one person are unnoticed by another. Often 

 odors and flavors charged to feed or cow are due to contamination of the 

 milk in the stable or elsewhere, after it is drawn from the cow. The 

 flavors and aroma of butter are mostly due to fermentation of milk 

 sugars, so that this matter rests only in part on feeding. 



568. The yellow color of cream and butter. It is common knowledge 

 that cows produce cream and butter which is more deeply colored in 

 summer when eating green feeds than in winter, and that Jerseys and 

 Guernseys usually produce a yellower product than the other breeds. 

 Extensive investigations by Palmer and Eckles at the Missouri Station 49 

 have at length shown that the color is due to a substance called carotin, 

 so named because it is the coloring matter of the carrot. This compound 

 is commonly found in green plants along with the green chlorophyll, 

 which masks its color. (8) It was found that animals given feeds 

 poor in carotin for long periods invariably produced white cream and 

 butter fat, regardless of the breed. This shows that the yellow color of 

 Jersey and Guernsey butter is not due to any ability of these breeds to 

 manufacture carotin. However, when cows of these breeds are given 

 feeds rich in carotin they transfer to their milk a larger part of the 

 yellow coloring matter of the feed than do cows of the other breeds, and 

 hence produce yellower butter fat. Green feeds in general were found to 

 be rich in carotin, as well as hay of a bright green color and new corn 

 silage. Carrots and other yellow roots also contain much of this coloring 

 matter. On the other hand, bleached hay, dry corn fodder or stover, 

 straw, old corn silage in which the carotin had been destroyed by fer- 

 mentation, corn, both yellow and white, and all the common concentrated 

 by-products, such as wheat bran, linseed meal, brewers' grains, etc., 

 were found to be poor in carotin. This explains why cows usually pro- 

 duce light-colored butter in winter. The color of yellow corn is due to 

 a colored substance other than carotin, which does not pass into the 

 milk. 



The yellow color of the body fat and skin of Jerseys and Guernseys 

 was found to be due to carotin. This shows why cows of these breeds 

 yield a highly colored product for a long time after going on winter 

 feed. During such periods the yellow coloring matter in their body fat 

 is transferred to the milk. Purchasers often discriminate against beef 

 having deeply colored fat, yet this tallow is colored by the same sub- 

 stance that gives butter the highly desired yellow color. 



"Mo. Res. Buls. 9, 10, 11, 12; also Cir. 74. 



