ANNUAL I'EKSISTKNCV AND KCtl I'HODrCTION 



15. Corn Uittdii Between Ainntal I'rodiictioii mnl .tinniiil Pernisteiiri/. 



201 



Other coiulitions being etpiiii, ;miv iiuTease in persisteney should l)e .iccoin- 

 panied Ity an inerease in annual ejrfr yield. These are i)urely 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 217!) individuals is tabulated, using ten-day classes for production, 

 to obtain the following constants: 



Number of birds ....... 2179 



Mean annual production ...... 177.16 



Production standard deviation .... ±44.73 



Mean annual persistency ..... 300.47 



Persistency standard deviation .... ±62.64 



Coefhcient of correlation +.7082±.0072 



Regression production on jicrsistency . . . -{-.506 



Regression jiersistency on {production . . . -(-.992 



The ai)ove coelticient rc\eals an intimate correlation between annual egg 

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

 furnish definite evidence to conunend 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 Hii/h 

 Persistenci/. 



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 



Above population mean i 872 | 280 



. \ , \ 



Below popidation mean j 264 | 763 



L__ \ 



I I 



Totals I 11.36 I 1043 



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 ])ersist- 

 ency as being closely associated with high annual fecundity. High ])ersist- 

 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. Siiould 

 high persistency breed as a true recessive, it would be a com])aratively simple 

 matter to establish the characteristic in the laying flock. 



