ANNUAL MOLT AND EGG PRODUCTION 79 



egg production, it is desirable to know whether persistency is related to 

 duration of molt. The population studied consisted of 929 birds with a defin- 

 ite molt period and a persistency record. In the majority of cases the onset 

 of molt marked the termination of the persistency record. There were, how- 

 ever, a considerable number of cases where the persistency record ended 

 with a cessation of egg production of 30 days or more and the period of non- 

 production associated with complete molt began after the bird had agaiji 

 l)een in production. 



The correlation between annual persistency and length of molt period was 

 made up using 15-day class intervals for persistency and 10-day class inter- 

 vals for molt period. The following constants were arrived at: 



Number ~of birds „ — 929 



Mean length of molt period — days — 75.60 



Molt period standard deviation — days ±30.38 



Mean annual persistency — days 339.95 



Persistency standard deviation — days ±36.57 



Coefficient of correlation —.2872 ± .0203 



Correlation ratio .3613 



Annual persistency ranged from a mininmm of 67 days to the highest pos- 

 sible maximum of 365 days within a single laying year. The magnitude of its 

 standard deviation indicates that its range of variability was not greatly 

 different from that observed in molt period. There were 809 genetically per- 

 sistent birds in the popidation and 120 genetically non-persistent individuals 

 CHays, 1927). The persistent group had a mean molt period of 72.94 days, 

 and the non-persistent group 93.50 days. This fact indicates that high phys- 

 iological activity characteristic of persistent layers was associated with a re- 

 duced molt period. 



The coefficient of correlation of ^.2872 ± .0203 is slightly below the min- 

 mum of .30 adopted for significance in these studies. The correlation con- 

 stant suggests that highly persistent or late molting hens in general seemed 

 to require a shorter period for molting than was required by less persistent 

 individuals. 



The correlation ratio of length of molt period to persistency was .3613. 

 By Blakeman's tests, (.3613)=— (.2872)^ = .0480 ± .0093. The difference be- 

 tween the correlation ratio and correlation coefficient is 5.16 times its prob- 

 able error, which indicates that the relationship between molt and persistency 

 was non-linear. Therefore, the correlation ratio of .3613 expreses the true 

 relationship between these characteristics. The data here used seem to point 

 to a significant negative correlation between length of molt period and an- 

 nual persistency. The X* method showed a probability of only .0011 that the 

 regression line for duration of molt on persistency was a straight line, which 

 further confirms the value of the correlation ratio over the correlation co- 

 efficient. 



Physiological Activities 



7. Weight at First Egg versus Lmigth of Molt Period. 



Records are available on weight at first pullet egg and length of molt for 



