CROSS-BREEDING 245 



should not be confused with cross-breeding. Cross- 

 breeding is the union of two or more distinct races or 

 breeds, while grading is an attempt gradually to develop 

 a type by continually breeding to pure-bred sires. 



Grading is one of the most successful and certain 

 methods of improvement. There are many examples 

 of successful grading among the breeders of domestic ani- 

 mals. Manifestly the more inferior the foundation mother 

 stock, the greater will be the improvement when mated to 

 a pure-bred registered sire. A few generations will often 

 suffice to produce " high-grade " cattle, horses, sheep or 

 swine that will possess most of the valuable qualities 

 which have commercial value. For commercial or eco- 

 nomic purposes, the high-grade beef animal may be as 

 valuable as the pure-bred. A high-grade dairy cow will 

 often produce as much milk and butter as the registered 

 cow. For breeding purposes, the pure-bred registered 

 animal is far superior. The grade does not transmit its 

 qualities with certainty. One object of pure breeding 

 is to develop the quality of prepotency, and this is accom- 

 plished by long years of most careful selection and mat- 

 ing. The grade animal cannot possibly possess the 

 quality of prepotency to the same extent as the pure- 

 bred form, hence it follows that even if the grade does 

 exhibit a high degree of individual merit, this is no evi- 

 dence of ability to transmit the same qualities to the 

 offspring. A high degree of individual excellence in a 

 pure-bred registered animal is more certain to be trans- 

 mitted, and for this reason the registered animal of high 

 merit is often held by the experienced breeder at values 

 which seem beyond any real economic basis. 



229. Cross-breeding to increase fertility. Some ani- 

 mals are infertile when bred to other individuals of their 



