PRINCIPLES OF SWINE BREEDING 23 



occurrence of malformations of various sorts. The re- 

 sults of inbreeding are different with different strains and 

 breeds. That inbreeding has a place in our breeding 

 practice is indicated by the fact that it has been freely 

 made use of in the formation of practically all of our 

 improved breeds of swine. In the hands of the right 

 man it can be used to good advantage. 



Line breeding. This is a term that is applied to one of 

 the methods often employed by breeders to fix a certain 

 type or character on their animals. Most breeders of 

 pure-bred hogs are line breeders, for they endeavor to 

 breed along a certain line. Line breeding resembles in- 

 breeding, but it is not so drastic. It has virtually the 

 same effects as inbreeding in fixing characters and estab- 

 lishing types, but it acts slower. As in inbreeding, it 

 may result in loss of vigor, size and fertility when carried 

 out without using sufficient judgment. Line breeding 

 has the opposite effect from cross-breeding. In practice 

 it consists of the continued use of the blood of some par- 

 ticular individual or strain of individuals in trying to 

 stamp or fix a certain character into the herd. This 

 method of improvement also has its drawbacks, for while 

 we are establishing some good characteristics we may 

 also be fixing and magnifying undesirable qualities. 

 Good examples of this are seen in those extremely well- 

 bred animals that in reality do not have the individuality 

 to merit registration. Nevertheless, in spite of its Draw- 

 backs, our most successful breeders have made free use 

 of it. At present it is about the quickest way we have to 

 magnify and fix a character. The main thing is in know- 

 ing the character and in realizing its value, and to have 

 the courage and conviction to stick to the character once 

 it is known. 



