No. 6. 



DEPARTMENT OF AGlllCULTUHE. 



557 



milk iu the form of an emulsion. There is no difference in the com- 

 position of the fat in the hirge and small {.^lobulea 



(6.) Amount of Fat in Milk. — The amount of fat present in normal 

 milk varies greatly, going, m the case of single milkings of individual 

 LOWS, below 2 per cent, and above 10 per cent. The average of fat 

 in the milk of herds of cows varies commonly between the limits of 

 3 and 5 per cent. The average amount of milk-fat in milk produced 

 in the United States, taking the true average for an entire year, 

 lies between 3.75 and 4 per cent., and somewhat nearer the latter 

 figure. 



Maiiy of the conditions that affect the amount of fat iu milk have 

 been studied and are w-ell established, w'hile others are but little 

 understood. We will consider briefly some of the better-known con- 

 ditions. 



(a.) Individuality. — It is uncommon to find iu a herd of cows au_> 

 two individuals whose milk contains the same per cent, of fat, 

 whether we consider individual milkings or the average of many 

 milkings. This is simply one of many factors that go to make a 

 cow's individuality. 



(h.) Breed. — It is v>ell known that the per cent, of fat in milk 

 varies in a more or less characteristic way with the kind of breed. 

 While there is marked variation in indivduals of the same breed, 

 there is found to be a fairly uniform difference, more or less marked, 

 if we take the average of several individuals. It is largel}^ owing 

 lO this influence that we find the milk of one country differing from 

 that of another, or the milk of one section of a country dift'ering 

 from that of another section. For example, the average per cent, 

 of fat in milk in Germany and Holland is fully one-half per cesat. 

 lower than in this country, because the prevailing breeds of cows 

 there are the oiies producing milk comparatively low in fat. The 

 figures given in the following table are taken from the records of 

 the Geneva (N. Y.) Station and represent averages of several indi- 

 viduals covering several periods of lactation: 



Holsteln 



Ayrshire, 



American-Holderness 



Short-Horn 



Devon 



Guernsey 



Jersey, , 



3.85 

 4.24 

 3.92 

 4.66 

 6.23 

 6.13 

 (.09 



