462 



PRINCIPLES OF AGRICULTURAL CHEMISTRY 



The best cow gave twice as much fat and milk as the poorest. 

 Some cows are very profitable, while others are fed at a loss. It 

 is important to test the individuals of a herd; the unprofitable 

 animals should be sold, and the feed of the others adjusted to the 

 quantity of milk produced. 



Fluctuations. The amount and composition of the milk from 

 the same cow may vary considerably from day to day. Thus, 

 Fleischmann 1 found by daily measurement and analysis, that the 

 amount and composition of the milk from the same cow, varied 

 as follows : 



The table shows a variation of nearly 25 per cent, between the 

 maximum and minimum for April, and 50 per cent, for 

 May. The milk from the other cows in the herd varied also, but 

 not on the same days, showing that the variations were not due 

 to factors which influenced the entire herd alike, but to individual 

 differences. 



Period of Lactation. The amount of milk given decreases with 

 the time the animal has been giving milk, but the decrease 

 varies with the animal. With some cows the decrease is 

 regular and gradual, others give the same quantity for a long 

 time and then suddenly fall oft". The following table from 

 Fleischmann's experiments, shows how the milk may decrease 

 with period of lactation, and it also shows that the percentage of 

 fat increases. Cow No. I behaves somewhat differently from 

 1 Lanclw. Jahrbuch, 1891. 



