INTENSITY IN RHODE ISLAND REDS 3 



Relation of Age at First Egg to Egg Weight and Intensity 



1. Age at First Egg and March Egg Weight 



For pullets hatched in March and April, egg weights taken during the month 

 of March represent the maximum egg weight for the first laying year according 

 to the observations of many investigators. In this study, mean egg weights for 

 the month of March were recorded on 612 pullets representing six generations. 

 These birds were divided into two groups with respect to age at first egg: 212 

 individuals with an age range at sexual maturity from 140 to 179 days; and 400 

 birds with an age range from 1 80 to 269 days. The birds in the first group should 

 carry both genes E and E' for early sexual maturity according to Hays (1936). 

 The latter group should carry either gene E or gene E' alone. 



The very early maturing group gave the following constants: 



Number of birds 212 



Mean age at first egg — days 167.94 



Age standard deviation ±7.95 



Mean March egg weight — grams 59.95 



Egg weight standard deviation ± 4.19 



Coefficient of correlation + .1402 + .0454 



The above data show that the variability was very low both in age at sexual 

 maturity and in March egg weight. Regression of egg weight on age at sexual 

 maturity was linear. The coefficient of correlation was positive but of such low 

 magnitude as to give odds of but 19 to 1 of being significant. In view of this 

 fact it is reasonable to assume that in this very early maturing population March 

 egg weight was little influenced by age at first egg. 



The medium early maturing group gave the following constants: 



Number of birds 400 



Mean age at first egg — days 195.05 



Age standard deviation + 12.17 



Mean March egg weight — grams 60.85 



Egg weight standard deviation + 3.78 



Coefficient of correlation — .0748 + .0335 



Only 14 birds in this population of 400 were older than 219 days when they 

 laid their first egg, so that the mean age of the group falls at 195 days. Such a 

 mean value may be considered representative of a population carrying either 

 gene E or gene E' alone (Hays, 1936). March egg weight was heavier than that 

 obtained in the extremely early maturing group, probably owing largely to 

 greater body weight. Regression of egg weight on age at first egg was strictly 

 linear. The coefficient of correlation was negative, but was of such small magni- 

 tude as to have no statistical significance. 



In general, our data show no relation between age at sexual maturity and the 

 mean weight of eggs laid by pullets at about eleven months of age. 



2. Age at First Egg and Winter Clutch Size 



It seemed desirable to confirm previous observations on Rhode Island Reds 

 that age at sexual maturity is negatively correlated with winter clutch size. 

 Hays and Sanborn (1927a) reported a correlation of —.2273 + .0103 between 



