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BULLETIN 905, tf. S. DEPARTMENT OE AGRICULTURE. 



vigor and a basis for further improvement. The great body, even of 

 the owners of purebreds, however, will own stock which is distinctly 

 below the best of its breed. For them improvement and fixation of 

 type can go hand in hand. The method is the consistent use of pre- 

 potent males of a given superior line. 



GRADING UP. 



Common stock can be improved and fixed in type by the same 

 methods as those described last. The process in this case is known 

 as grading up. Even two or three crosses with superior purebred 



Fig. 12.— A Merino ram, an example of the flue-wool type of sheep. 



males should raise the level practically to that of the average pure- 

 bred, if not better, so far as individual qualities are concerned. With 

 five or six such crosses it would doubtless be possible to produce 

 animals better than most purebreds both in their own characteristics 

 and in their breeding power. 



It is not, however, considered practicable to permit registration of 

 grades as purebreds, no matter how many top crosses there may be, 

 with superior purebred males of the same breed. In all but this 

 respect, however, a large stock of common females can be rapidly 

 converted into a herd as good as a purebred herd by grading. It is 

 in the grading up of the common stock of the country that scientific 

 breeding can render its greatest service. 



