BREEDING 117 



of these tend automatically to produce purity in a given 

 character. 



If only individuals of the highest constitutional vigor are 

 used, improvement will be found still more satisfactory if 

 the pure-bred males used from year to year are members 

 of the same family as well as members of the same breed. 

 The reasons for this are discussed under "line breeding." 



Banger of Grading. — ^The weakness of grading as a practice 

 lies in its success as a method. Because in the second or 

 third generation males are produced that very closely 

 approach standard, line-bred birds in appearance, the temp- 

 tation is to use them for breeding purposes rather than to 

 purchase, first cost considered, a relatively expensive stand- 

 ard-bred bird. When this is done improvement usually 

 stops and the ground gained will be at least partially lost. 



Thus, if in Fig. 51 the offspring of C and D appear to be 

 fairly uniform, the breeder may yield to the temptation to 

 use a fine-looking cockerel from group E. The offspring 

 on the average carry 25 per cent, mongrel blood instead of 

 12.5 per cent., as indicated at Gand is therefore no improve- 

 ment over E. In fact, in appearance many of them will not 

 be as good, because the offspring E has the benefit of the 

 characteristics transmitted by a standard-bred sire. A 

 grade sire is no more prepotent than the grade females he 

 is mated with. The result is that instead of tending to becoihe 

 more uniform the offspring will be less so. 



Cost of Pure-bred Sire for Grading. — ^The per chick cost 

 of furnishing pure-bred sires is determined to a considerable 

 extent by the persistence and success with which the pro- 

 ducer selects his breeding females. Figuring on the conserva- 

 tive basis of mating but twelve hens to one male, of securing 

 a 885 per cent, production during the breeding season, and 

 of setting four eggs for each chick raised to maturity, the per 

 chick cost of furnishing a pure-bred male that cost five dollars 

 would be five and a half cents. 



In comparison with these figures the results of some unpub- 

 lished experiments at the Kansas Station are significant. 

 A standard-bred Single Comb White Leghorn male purchased 

 from a production-breeder, was mated with ten mongrel 



