174 DAIRY FARMING 



It will be noted that the main variation is in the fat, al- 

 though the protein -shows sufficient variation to be of impor- 

 tance. Sugar varies but slightly, and the ash practically 

 none. The breed of the cow also has a marked influence 

 upon the size of the fat globules. Those of the Jerseys and 

 Guernseys are much larger than those of the Holsteins. The 

 larger fat globules in Jersey milk result in quicker and more 

 complete separation of the cream by gravity ; also in a slight 

 difference in the ease of churning. The breed of the cow 

 likewise has a marked influence upon the color of milk and 

 especially upon the color of the butter. In amount of color 

 the Guernsey ranks first, followed by the Jersey, Short- 

 horn, Ayrshire, and Holstein in the order named. There 

 is no basis for the common claim that certain breeds pro- 

 duce milk or butter of a better flavor than others. Out- 

 side the possible variation in color, the most expert judge 

 cannot distinguish the product of one breed from that of 

 another when other conditions are the same. 



162. Stage of Lactation. The stage of lactation stands 

 second only to the breed in importance as a factor influencing 

 the composition of milk. The amount of the different con- 

 stituents and also the nature of the fat itself is influenced in 

 this way. The most marked effect is upon the amount of 

 protein and fat. 



The figures in Table 21 obtained by the author show the 

 average for eleven cows representing three breeds which were 

 kept on a uniform ration for an entire lactation period to elim- 

 inate changes due to feed. A decided increase in the amount 

 of fat and protein is shown, but little change in the sugar 

 content. 



The stage of lactation also has a marked effect upon 

 the size of fat globules. After the cow has been in milk 



