THE BREEDING OF ANIMALS, IN GENERAL 93 



both sire and dam. It is inferior to either of the other two in 

 strengthening characters, and is not so safe because nothing is 

 known of the breeding of either parent. 



There are many advantages that follow this system of breed- 

 ing: it intensifies characters, gives stability to the family, 

 increases the prepotency, and favors uniformity. In-breed- 

 ing results in the highest possible percentage of the desired blood 

 being retained in the offspring, and is therefore recognized as the 

 strongest of all breeding. It also gives rise to the simplest 

 form of pedigree. Since the infusion of new strains shatters 

 existing characters, no system equals in-breeding for perpetu- 

 ating characters, doubling up existing combinations, as well 

 as retaining all there is of good in the exceptional individ- 

 ual. Capable of producing the great improvement that it 

 is, in-breeding is not without its disadvantages. It does not 

 respect characters; it does not separate the good from the bad, 

 but intensifies both good and bad alike. In-breeding, if per- 

 sisted in, results in loss of fertility as well as vigor, which may 

 quickly lead to race extinction. These are two most common 

 defects resulting from this method of breeding, and they come 

 about naturally. Few animals are regular breeders, and a still 

 fewer number are both vigorous and regular breeders. Hence, 

 when such animals are in-bred, the tendency is still farther to 

 lower both the vitality and the fertility. When practicing 

 this method, therefore, too much cannot be made of selecting 

 for high fertility and much vigor. 



There are two situations under which it may be desirable to 

 practice in-breeding. One is in grading, where, if we have a 

 proved sire, one that is known to get excellent offspring, it may 

 be entirely permissible to mate him with his own daughters 

 rather than to procure a new sire, in which the breeding power 

 is not known. Again, such an exchange of sires as would be 

 necessary to prevent in-breeding often calls for a considerable 

 outlay of time and money. 



