HOW INDIVIDUAL SELECTION IS MADE 



135 



age fat content double that of another in the same breed, but 

 such extremes would be very exceptional. In a pure-bred 

 herd the average per cent of fat seldom varies more than one 

 fourth from the lowest to the highest. The fat content of the 

 milk of each individual cow becomes of more importance when 

 herds of mixed breeds are used than is the case where the blood 

 of one breed predominates in all. This comes about on ac- 

 count of the wide variation in fat content between breeds ; and 

 in animals of mixed breeding it is impossible to tell without 

 testing what characteristic has been inherited regarding the 

 fat content of the milk. 



TABLE 6 



RELATION OF PER CENT OF FAT TO TOTAL FAT PRODUCTION 

 UNIVERSITY OF MISSOURI HERD 



In communities where milk is sold to factories on the butter- 

 fat basis certain herds are often considered the best in the 



