SELECTION OF THE HERD BULL 161 



dams. The herd was deteriorating rapidly as long as he 

 stood at the head. 



These results show the immense difference in the way dairy 

 qualities are transmitted, even where both sire and dam are 

 pure-bred animals, and how serious a problem is the selection 

 of a herd bull for the man who is trying to further improve 

 a herd of pure-bred animals already well developed. 



Cause of the Variation in Transmission of Dairy Qualities. 

 One of the chief difficulties in regard to selecting the bull 

 is that practically nothing can be predicted from the looks of 

 the animal as to how he will transmit dairy qualities. The 

 man who will discover some means of so selecting the bull 

 will confer a benefit on breeders that can scarcely be esti- 

 mated. 



There are two principles that are especially concerned 

 with breeding, which should be kept in mind. The first is 

 that "like produces like," and the second is the law of 

 "natural variations." 



The cow, in the condition nature made her, undoubtedly 

 produced only milk enough to feed the calf a few months until 

 it could subsist on other foods. This milking characteristic 

 was transmitted quite regularly. It was a case where like 

 generally produced like; but some cows even then were un- 

 doubtedly better milkers than others, due to the law of natural 

 variation. The principle of selection did not come in to 

 retain these variations, and no improvement in this char- 

 acteristic was made. 



After cattle were domesticated, the same conditions ex- 

 isted, but finally man began taking advantage of the natural 

 variations, and saving breeding stock from those having the 

 characteristics, such as great milk production, which were 



