122 POULTRY PRODUCTION 



iiiatiiii;' I'roni groiii) (' sIidwii at 11 ^\•itllullt, however, liaviug 

 tlieiii (lireetl)' connected genetically. 



])iiu(jrr of Liiir llrrcdiiig. — As in t;Ta(ling, danger lies in 

 the temptation to use as a breeder a grade male tliat "looks 

 good", so in line hreeding the danger lies in trusting in the 

 elhcaey (if line breeding, in and of itself, and in continuing 

 to mate relati\'es after they have ceased to "look good." 

 Inlireediiig in any form offers opportunity for the segre- 

 gation of characters, thereby not infrequently disclosing 

 recessive poor cpialitics as well as tending to render pure, 

 doiniiiant desirable qualities. Idiis increases directly with 

 the closeness of inbreeding, the closest possible being that 

 of a brother and sister mating as showii at C and J{ in 

 h'igure '>'■>. 



Vvw fowls are fully fertile and fewer still are both fertile 

 and vigorous. Selecting relatives both of which approach 

 perfection in physiciue is difficult. ^lany weaknesses are hid- 

 den, only to be discovered by disappointing experience. It is 

 easy to mate individuals of a greater or less relationship 

 where an inisuspected mutual tendency toward infertility 

 will be disclosc<l. It is all too common to mate fowls with a 

 more or less common ancestry, which already sliow the warn- 

 ing earmarks of a weakened constitution. The result can 

 hardly be otlier than a progeny that is weaker than either 

 parent. 



Cole and Ilalpin' began inl)reediiig Rhode Island Reds 

 in I'.ll.'i making sonic matings as close as Iirothcr and sister. 

 'J'he selection prai'ticed was for color and birds of wonderful 

 color were ])roduccd. The ]ier cent of fertile eggs liatched, 

 however, decreased ra])idly as shown by the folloA\ ing ffgures. 

 In lili:;, (17 ])er cent of the fertile eggs hatched. In 1014 the 

 per cent was 1(1. In I'.ll.") it was 41 ])ei- cent and in IDlCi 

 bS per cent. In 1017 not a chick could he hatched. 



In 19bS a new phase of the ex|)ei'imeiit w as initiated. T lose 

 inbreeding was maintainccl as before, but the selection was for 

 vigor. This ])hase lias been in ])i'ogrt'ss but two vears. 

 There is S(i far no indication of a rapid decrease in fertility 



1 P.iiiitrj- ( 'ulluiv, Ahir.'li, 1!I2I1. 



