CHAPTER VI. 



VARIATION OF FAT IX MILK. 



The percentage of fat in normal milk varies a great deal 

 more than any other of the constituents of milk. Dr. Rich- 

 mond reports that the fat of milk may go as low as 1.04:% and 

 as high as 12.52"^,. Such exti-cnio variations are, of course, 

 abnormal. The fat-content seldom falls below 2^-% or rises 

 above T'/c- The fat-content of milk from a wliole herd of 

 cows, varies only within comparatively narrow limits. The 

 following are the chief factors which cause the fat-content 

 of milk to vary: 



(1) Individuahty of cows. 



(2) Breed of cows. 



(3) Time between milkings. 



(4) Manner of milking. 



(5) Whether the milk is fore or after milk. 



(6) Age of cow. 



(7) Lactation period. 



(8) Feed of cows. 



(9) Environmental conditions. 



I. Individuality of Cows. — That the quantity of milk from 

 individual ccms varies is a fact that is well known to every- 

 one who keeps cows, but the average co^'-keeper does not very 

 well apprehend that the percentage of fat is as variable a factor 

 as it really is. As a rule, when a cow yields only a small quantity 

 of milk she is in many instances condemned without taking 

 the quality into consideration. If the fat content were taken 



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