246 PRACTICE OF POULTRY BREEDING 



BREEDING SYSTEMS. 



Crossbreeding or Hybridizing.^Crossljreeding may be defined 

 as the breeding together of birds of different breeds, varieties, 

 or families, with the hope of securing progeny exhibiting in one 

 individual the desirable characteristics of both parents. This form 

 of breeding is only applicable in the formation of new breeds. 

 The effect of its use is so thoroughly to mix blood lines and pedi- 

 grees that all records of the performances of the ancestry are lost 

 or of no value. Crossing is one of the most certain means of pro- 

 ducing variability. 



Where birds possessed of similar characteristics are mated 

 together, the progeny of the first cross usually show a fair degree 

 of uniformity with regard to the desired trait. Further breeding 

 of this crossbred progeny, or hybrid, will result in a great variety 

 of types and variations in the characteristics. 



When birds of opposite or unlike characters are mated together, 

 the results are varied and disappointing, even in the first generation. 



A good rule is to avoid crossing wherever possible, and to 

 resort to it only as the last extreme toward a definite aim. 



Grading up is a term applied to a method quite generally used 

 to improve the quality and characters of a mongrel flock. This 

 is usually accomplished by the use of pure-bred males in a mixed 

 flock. The resulting progeny are called grades, since they are the 

 offspring of a pure-l^red animal and one of mixed or common breed- 

 ing. In poultry raising the cost of birds which are pure bred and true 

 to type is relatively so small, in comparison with their superiority 

 over mixed stock, that, as a rule, it is more satisfactory and econom- 

 ical to begin with pure-bred birds, and if need be to start with but 

 a small number. Where grading up is practised, the mating may 

 be made either way, but the male is generally taken for the pure- 

 bred parent, since he represents half the flock as far as progeny are 

 concerned. By this method it is possible to raise a practically 

 pure flock from mongrels in a certain number of generations. 



The great disadvantage of grading up is the fact that it is noc 

 likely to be closely followed continuously after a certain degree 

 of perfection is reached, and, just as soon as the breeder uses a 

 grade male bird, improvement ceases and retrogression begins. 



Inbreeding. — The terms inbreeding and in-and-in breeding 

 are used to designate the breeding together of animals which are 

 of the same pedigree. Inbreeding commonly means the mating 



