10 MASS. EXPERIMENT STATION BULLETIN 313 



The two populations showed a significant difference in mean weight at first 

 egg. It seems evident, therefore, that lack of body weight at sexual maturity is 

 in part responsible for small egg size in the population that failed to reach standard 

 egg weight. 



Larger winter clutch size stood out in the small-egg population compared 

 with the large-egg population. Extreme winter intensity accounted in part for 

 the failure of one population to attain standard egg size. 



The two groups of birds were identical in mean pause duration, and the small- 

 egg group showed 59 per cent with winter pause compared with 62 per cent in 

 the other group. 



The small-egg group showed more intense broodiness, but the percentage of 

 broody birds was essentially identical in the two populations. 



In persistency, the small-egg group showed a significantly lower mean than the 

 large-egg group. This fact appears to suggest that low persistency was in part 

 responsible for small egg size. 



The small-egg population showed slightly higher winter production and the 

 same annual production as the large-egg group. The fact is therefore evident that 

 number of eggs is not a factor governing egg size. 



The group failing to reach standard egg weight gave a decidedly lower annual 

 egg weight than the other group. The small-egg group gave an annual egg weight 

 average of 21.1 ounces per dozen compared with 23.5 counces for the large-egg 

 group. 



SUMMARY 



A study of the records of Rhode Island Red pullets hatched over a five-year 

 period, where every egg was weighed from the trapnest, leads to the following 

 deductions with respect to characters affecting the time interval between first 

 pullet egg and standard egg weight or the failure to attain standard egg weight 

 during the first laying year. 



1. Early hatching greatly increased the time to standard egg weight. 



2. Extreme early maturity within a genetically early-maturing population 

 tended to greatly increase the time interval to standard egg weight. 



3. Small body weight at first egg also increased the time interval but to a 

 lesser extent than hatching date or age at sexual maturity. 



4. Very high winter intensity was associated in some degree with a longer 

 period to standard egg size. 



5. Pause duration had little or no effect on the time interval. 



6. Intense broodiness prolonged the period to standard egg weight. 



7. High persistency very greatly reduced the time to standard egg weight. 



8. High winter egg production slightly increased the time interval, but high 

 annual production had no effect. 



9. Annual egg weight was intimately negatively association with the time 

 interval to standard egg weight. 



