FACTORS AFFECTING EGG PRODUCTION 11 



In general, the data in table 1 emphasize the need of increasing the intensity 

 in spring, summer, and fall. To a lesser extent the shortening of spring and sum- 

 mer pauses offers opportunities. Since the present level of egg size is satisfactory, 

 no change in this character would seem to be desirable. From the standpoint of 

 selective breeding, it seems desirable to add the following to the list for selective 

 purposes: High spring, summer, and fall intensity and short spring and summer 

 pauses. 



SUMMARY 



An attempt has been made to measure the eflfects of sixteen factors on annual 

 egg production. The study included records on 1470 Rhode Island Red females 

 bred for high fecundity and hatched from 1937 to 1942. The following deduc- 

 tions seem to be warranted. : 



1. Hatching date within the range used showed no significant correlation 

 with annual egg production. 



2. Annual production exhibited a non-linear regression on age at sexual 

 maturity. The association was negative, with a correlation of .2264. 



3. Body weight at first egg showed a small but significant negative correla- 

 tion with annual production. 



4. High winter intensity as measured by clutch size had an intimate associa- 

 tion with annual production, although regression was not strictly linear; high 

 spring intensity was slightly more intimately associated with annual production 

 than winter intensity, regression again being non-linear; and summer clutch size 

 was more important than either winter or spring clutch size as measured by the 

 correlation ratio with annual egg record. Clutch size was least important in the 

 fall, but its relation to annual egg production was still very significant. 



5. Duration of winter pause, in the part of the population having winter 

 pause, showed an important negative correlation with annual egg production; 

 spring pause duration was of greater importance than winter pause duration; and 

 summer pause duration was more intimately negatively correlated with annual 

 production than pauses in either winter or spring. 



6. There was no correlation between the number of broody periods and 

 annual production in the small population of broody birds. 



7. Annual persistency was intimately associated with yearly egg production. 



8. There was a moderate positive association between time to standard egg 

 weight and annual production. 



9. Larger egg weight in March had a significant tendency to reduce the 

 number of eggs laid in the year; but a moderate positive correlation showed that 

 annual egg weight and annual egg production tended to increase together. 



10. There was a moderate negative correlation between body weight at the 

 close of the first laying year and annual production. 



11. The data indicate that, among the different characters studied in relation 

 to egg production, intensity of lajang in summer and fall offer good possibilities 

 in selection. Pauses in production in winter, spring, and summer should also 

 be carefully selected against in breeding stock. 



12. Evidence is submitted to indicate that the sixteen different characters 

 considered offer a very good working basis upon which to direct future breeding 

 operations. 



