ANNUAL PERSISTENCY AND EGG PRODUCTION 2OI 



15. Correlation Between Annual Production and AnnxMl Persistency. 



Other conditions being equal, any increase in persistency should be accom- 

 panied by an increase in annual egg yield. These are purely quantitative rela- 

 tions and in this manner some information concerning the value of high per- 

 sistency from the fecundity standpoint may be ascertained. The same popu- 

 lation of 2179 individuals is tabulated, using ten-day classes for production, 

 to obtain the following constants: 



Number of birds 2179 



Mean annual production 177.i6 



Production standard deviation .... ±44.73 



Mean annual persistency ..... 300.47 



Persistency standard deviation .... ±62.64 



Coefficient of correlation -f .7082±.0072 



Regression production on persistency . . . -)-..506 



Regression persistency on production . . . -(-.992 



The above coefficient reveals an intimate correlation between annual egg 

 yield and annual persistency or the length of the laying year. These data 

 furnish definite evidence to commend the practice of emphasizing late molt- 

 ing in breeding for high fecundity. On the average, any increase in persist- 

 ency within the limits of the pullet laying year is advantageous. 



16. Correlation Between Annual Production Above the Mean and Hif/h 

 Persistency. 



By classifying all birds as high producers if they laid more eggs than the 

 population mean of 177.46, and as high in persistency those birds that laid 

 for not less than 315 days before molting, a definite relation between high 

 production and high persistency may be established. 



Annual Production | High Persistency | Low Persistency 



I \ 



I I 



Above population mean I 872 | 280 



\ \ 



I I 



Below ]i()])ulation mean I 264 | 763 



I \ 



1 I 



Totals I 1136 I 1043 



I I 



Coefficient of correlation -f.8000±.0052 



The above coefficient of correlation establishes a very intimate relation be- 

 tween the presence of possible genetic high persistency and annual egg yield 

 above the average of the total population. This fact points to high persist- 

 ency as being closely associated with high annual fecundity. High persist- 

 ency must, therefore, be classed as a trait of vital importance in breeding for 

 fecundity and one that .should be stressed greatly by the breeder. Should 

 high persistency breed as a true recessive, it would be a comparatively simple 

 matter to establish the characteristic in the laying flock. 



