PRINCIPLES OF SWINE BREEDING 39 



offspring of parents from different breeds, and that it is 

 not necessary that the parents be pure bred, but they 

 must be very high grade. Others state that an animal is 

 a cross-bred when the sire and dam were both pure bred, 

 but belong to different breeds. 



Under certain circumstances it may be well to cross 

 two breeds, but the cross should never be carried farther 

 than one generation. In the second generation the tend- 

 ency is for various characteristics to Mendelize and split 

 off, and the resultant great variation is decidedly detri- 

 mental. Therefore, if we do any crossing at all, we 

 should not carry it farther than the first generation. It 

 is true that swine breeders and pork growers in general 

 attach great value to crossing breeds, claiming greater 

 vigor, quicker maturity and larger and stronger bone. 

 These advantages are to a large extent only apparent, 

 and experimental evidence shows the advantages to be 

 so slight as not to justify the crossing as a regular prac- 

 tice. Breeds should only be crossed, therefore, when hogs 

 are to be grown for the market. Most any breed will 

 cross up well with other breeds, but crossing is usually 

 not advisable, and should only be carried out under 

 exceptional circumstances. 



Prepotency of pure-bred boars. — Pure-bred boars seem 

 to possess a certain prepotency and ability to stamp their 

 type that is not possessed by scrub or grade boars. This 

 is very much in evidence where a pure-bred boar is used 

 on a few native sows, in which the pigs of the first gener- 

 ation are apparently almost full blooded. This ability to 

 stamp type on the offspring is not possessed by the scrub. 

 This characteristic of pure-bred swine is undoubtedly due 

 to long and continued line inheritance as a result of 

 selection. The type of the pure bred we might say is 



