BREEDING FOR EGG PRODUCTION 13 



housed and continue for one year. The causes of mortalit}' have been grouped 

 into fourteen general classes, and the original number of pullets housed was 751. 



Per cent 



Ruptured or obstructed oviduct 2.53 



Ruptured egg yolks, peritonitis 1 . 33 



Tumors 2 . 93 



Worms : 1.86 



Leukemia 3 . 20 



Visceral gout, nephritis 2.26 



Impaction 1 . 20 



Paralysis 2 . 66 



Chronic coccidiosis 27 



Prolapsus 93 



Cannibalism 6.79 



Injury 67 



Miscellaneous 4.13 



No recognized cause 9 . 99 



Total loss 40 . 75 



Examination of these records does not point to an>' specific diseases as pre- 

 dominant causes. The greatest percentage of birds died from miscellaneous 

 causes not common in the flock. Almost 10 per cent of birds showed no specific 

 cause on post mortem. Leukemia, tumors, parahsis and ruptured or obstructed 

 oviduct appear as most potent specific disorders in the flock. The loss of 6.79 

 per cent from cannibalism cannot be due to lack of \'igor but is probably due 

 entirely to faulty management. 



From the standpoint of breeding to reduce mortalit}-, the logical procedure is 

 to select breeders from families with the lowest mortality. Neither breeding 

 males nor breeding females should be used from families with a greater mortality 

 than 10 per cent between hatching and housing in the fall. The yearly mortality 

 in pullet families in the laying houses should not exceed 15 per cent including 

 those culled. The mortality from housing time in the fall tip to the breeding 

 season in February or March should not be greater than 5 per cent. 



The Influence of Inbreeding 



Inbreeding is a useful tool of the breeder in securing uniformity because the 

 mating of closely related individuals tends to increase homozygosity. This 

 method of breeding has been extensively used in developing new breeds and 

 varieties where the chief concern is uniformity in type and plumage character 

 and color. 



Inbreeding in production-bred flocks has not gi\'en encouraging results accord- 

 ing to the work of a number of investigators. Dunn, Hays, Dunkerly and Jull 

 have all reported that inbreeding decreases egg production. Extensive studies 

 by Hays (1929b) show the following undesirable results from inbreeding Rhode 

 Island Reds: sexual maturit>- was retarded, winter pause increased, intensity 

 lowered, persistency lowered, egg production decreased, fertility lowered, hatch- 



