32 



Farmers' Bulletin 1167. 



fixity of type appears. Continued use of males of the same breed 

 results, in a comparatively short time, in animals which are practi- 

 cally purebred, although not eligible to registration and therefore not 

 salable as purebreds. 



In grading up, consistent methods should be used and males of the 

 same breed used, cross after cross; otherwise the stock will be mon- 

 grelized instead of improved. Males should also be better indi- 

 viduals in all respects than the females with which they are mated, 

 in order that each successive cross may be an improvement over the 

 ones which went before it. 



Uniformity Quickly Obtained by Use of Purebred Males. 



FIG. 27. Kids at the Experiment Farm of the Bureau of Animal Industry, Beltsville, 

 Md., by purebred Saanen bucks on foundation of native does. 



CROSSBREEDING. 



Crossbreeding is the mating of purebred animals of different breeds 

 of the same species. Crossbred animals are usually larger and more 

 vigorous than either parent. Their hereditary material, however, 

 is so complex that there is no certainty as to what results will come 

 from mating them. Except to produce market animals, crossbreed- 

 ing should be used only by the highly skilled breeder, and it is not 

 practicable in his case unless he has an opportunity to place the 

 progeny on the market for breeding purposes. American practice in 

 livestock breeding does not encourage the development of new breeds 

 except in the case of poultry and pet stock. Therefore the practical 

 man, as a rule, will leave this matter to the experimentalists. 



