FACTORS AFFECTING EGG PRODUCTION 7 



In the attempt to discover whether there was a significant correlation between 

 the number of broody periods and annual production in the small broody popula- 

 tion, the following constants appeared: 



Number of broody birds 56 



Mean number of broody periods 1.36 



Number of broody periods standard deviation +.72 



Mean annual production — eggs 212.18 



Annual production standard deviation +30.12 



Coefficient of correlation +.0009 + .0901 



The above data indicate that there was no correlation between the number of 

 broody periods and annual egg production in the small population studied. 



Persistency 



12. Relati on of Annual Persistency and Annual Production 



The work of many investigators has shown that persistency is one of the most 

 important characters affecting egg production. The term "persistency" as 

 used in this laboratory is concerned entirely with the length of the pullet laying 

 year. Biologically, persistency is circumscribed by sexual maturity at the 

 beginning of the year and by annual molt at the end of the year. It is our belief 

 that persistency is independent of the rate of laying. The population was 

 tabulated, giving the following constants: 



Number of birds 1470 



Mean annual persistency — days 338.33 



Annual persistency standard deviation +37.58 



Mean annual production — eggs 213.57 



Annual production standard deviation +43.38 



Coefficient of correlation +.4704 + .0137 



Correlation ratio .5194 



Since the regression was non-linear, the correlation ratio correctly measures the 

 association, which is a very intimate one and indicates that high persistency is 

 an extremely important character in its relation to annual egg production. 



Egg Weight 



13. Relation of Time to Standard Egg Weight to Annual Production 



The time to standard egg weight is measured by the number of days required 

 from the first pullet egg to the period in which a pullet lays five successive 56.7- 

 gram or two-ounce eggs. It is conceivable that a very rapid Increase In egg weight 

 might reduce the number of eggs laid and that a slow rate of Increase in egg weight 

 might be associated with a greater number of eggs. Records were secured on 

 1150 individual birds and the correlation was determined between this time inter- 

 val and annual egg production. The following constants appeared: 



Number of birds 1 150 



Mean time to standard egg weight — days 49.70 



Time to standard egg weight standard deviation +49.10 



Mean annual production — eggs 212.73 



Annual production standard deviation. . +43.29 



Coefficient of correlation +.0476 + .0198 



Correlation ratio .2111 



