VARIATIONS OF MILK CONSTITUENTS 157 



While many conditions cause the percentage of fat 

 in milk to vary, we will notice only three as of special 

 importance in connection with cheese-making: (i) 

 Breed, (2) stage of lactation, and (3) change from 

 barn to pasture. 



Influence of breed of cows on fat content of milk. 

 The influence of what is known as breed upon 

 the composition of cow's milk has been long recog- 

 nized and extensively studied in a general way, 

 but only in a comparatively limited way in its rela- 

 tion to cheese-making. It is largely owing to this 

 influence that we find the milk of one country dif- 

 fering from that of another, or the milk of one 

 section of a country differing from that of another 

 section. For example, the average percentage of 

 fat in milk in Germany and Holland is fully one- 

 half per cent lower than in New York state, and 

 probably in the United States at large, because the 

 prevailing breeds of cows there are those producing 

 milk comparatively low in fat. The results of 

 recent tests go to show that in Canada the milk 

 in Quebec province contains more fat than does 

 that of Ontario, since in the former the native 

 Jerseys are the predominant breed, while in the 

 latter, Holstein-Friesians, Ayrshires and Short- 



PERCENTAGE OF FAT IN MILK OF DIFFERENT BREEDS OF 



COWS 



Name of breed Per cent of fat in milk 



Holstein-Friesian 3.26 



Ayrshire 3.76 



American Holderness 4.01 



Shorthorn 4.28 



Devon 4,89 



Guernsey S.38 



Jersey 5.78 



