10 MASS. EXPERIMENT STATION BULLETIN No. 286 



PRACTICAL APPLICATIONS 



In breeding a flock for high intensity, the starting point is the selection as 

 breeders of those females laying in large clutches in March, April and May. 

 The next step is the selection of breeders with large spring clutch size and in 

 addition winter clutch size of not under three eggs. Because of the intimate cor- 

 relation between early sexual marturity and large winter clutch, it is also import- 

 ant that breeders carry early maturity. The third and final step in selection for 

 high intensity is the addition of high summer intensity from June first to the 

 close of the laying year. In order to establish uniform high intensity throughout 

 the pullet laying year it is necessary to employ yearling breeders that exhibit 

 large clutch size in winter, spring and summer. 



SUMMARY 



Intensity during three seasons of the pullet laying year is considered. Winter 

 clutch size measures the intensity from first pullet egg to March first. Spring 

 clutch size covers the period from March first to June first. Summer clutch 

 size includes the time interval beginning June first and continuing to the close 

 of the 365-day laying year. 



March clutch size, April clutch size and May clutch size are each studied as 

 possible short-time measures. 



Winter clutch size and spring clutch size show a non-linear relation and the 

 correlation ratio between the two is .417 L 



Winter clutch size and sununer clutch size also show a non-linear relation 

 with a correlation ratio of .309L 



Spring clutch size and summer clutch size show a linear relation to each other 

 and a coefficient of correlation of +.4593 + .0130. 



Winter clutch size is correlated to a high degree with age at first egg. 



The degrees of correlation between winter clutch size and winter pause dura- 

 tion, winter clutch size and days broody and winter clutch size and persistency 

 are very moderate but slightly significant. 



Spring clutch size shows non-linear regression on winter pause duration with 

 a correlation ratio of .3596. 



March clutch size, April clutch size and May clutch size are independent 

 of age at first egg, winter pause duration, total days broody and persistency. 



Summer clutch size is independent of age at sexual maturity, moderately 

 correlated with winter pause duration and persistency and correlated to 

 the extent of .3531 with total days broody. 



As a criterion of annual egg production, the six short-time measures rank in 

 the following order determined by the degree of correlation: spring clutch, 

 summer clutch, winter clutch, April clutch, May clutch and March clutch. 



In general, clutch size seems to increase somewhat following either a winter 

 period of non-production or a broody period. 



The mean clutch size for the flock studied was: winter, 3.35; spring, 4.07; 

 and summer, 3.04. 



The most significant short-time measure of intensity is spring clutch size, 

 but no short-time measure of intensity is as accurate as the mean clutch size for 

 the entire year. 



