6 MODERN METHODS OF TESTING MILK 



COWS two individuals whose milk contains the same 

 per cent, of fat, whether we consider single milkings 

 or the average of many milkings. 



(2) Influence of breed of coi^' on fat content of 

 milk. — It is well known that the per cent, of fat in 

 milk varies in a somewhat characteristic way with 

 the kind of breed of cow. While there is marked 

 variation in individuals of the same breed, there is 

 found to be a fairly uniform difference, more or less 

 marked, if we consider the averages of several indi- 

 viduals. It is largely owing to this influence that 

 we find the milk of one country differing from that 

 of another, or the milk of one section of a country 

 differing from that of another section. For example, 

 the average amount of fat in milk in Germany and 

 Holland is fully one-half per cent, lower than in this 

 country, because the prevailing breeds of cows there 

 are those producing milk comparatively low in fat. 

 The following figures, taken from the records of the 

 New York (Geneva) Agricultural Experiment Station, 

 represent averages of many individuals for several 

 periods of lactation: p^^. ^^^^^ ^f 



fat in milk 

 NAME OF BREED Average Lowest Highest 



Holstein Friesian . . . . . 3.36 2.88 3.85 



Ayrshire 3-6o 3-'0 424 



American Holdcrness .... Z-7Z 3-49 3-9^ 



Short Horn . 4-44 4-'8 4-56 



Devon 4-6o 4.30 5.23 



Guernsey 5-30 4-5 1 6.13 



Jersey 5-6o 4-96 6.09 



(3) Influence of a^e of cozv on fat content of 

 milk. — So far as published data throw light upon this 



