10 MASS. EXPERIMENT STATION BULLETIN 411 



Summary 



Relations between both annual and March variability in egg weight have been 

 studied in the ten previous sections of this report. 



A rather intimate negative correlation was observed between age at first egg 

 and annual variability in egg weight, indicating that the pullets that begin lay- 

 ing earliest are likely to show the greatest annual variation in egg weight. No 

 correlation, however, was observed between age at first egg and March variability 

 in egg weight. 



No correlation of significance was discovered between winter clutch size and 

 either annual or March variation in egg weight. 



Annual and March variability in egg weight were essentially equal in the pause 

 and non-pause populations; and in the broody and non-broody populations. 



Annual persistency and annual variation in egg weight were independent; but 

 birds showing highest persistency had a slight tendency to exhibit lower varia- 

 bility in egg weight for the month of March. 



Relation of Position of Egg in Clutch to Variability in Egg Weight 



The relation of position of egg in the clutch was first studied by Atwood and 

 Weakley (1917) using White Leghorns. These workers reported that the first 

 egg of the clutch was generally heavier than later eggs but that in large clutches 

 the rate of decrease was relatively slower than in small clutches. JuU (1924) 

 confirmed these observations using Barred Phmouth Rocks. Funk and Kempster 

 (1934) likewise obtained similar results with White Plymouth Rock pullets. 

 Hays (1934) pointed out that birds laying at a high rate required a longer period 

 to attain standard egg weight than those la> ing in smaller clutches. 



The relation of the position of the egg in the clutch throughout the first laying 

 year to variability in egg weight has been studied in this report. The data are 

 tabulated below: 



Table 2. — Rel.ation of Position of Egg in the Clutch to Egg Weight 



AND \'aRIABILITY. 



Position of Egg Number Mean Standard Deviation 



in the Clutch of Egg Weight in Egg Weight 



Eggs Grams Grams 



1 4409 62.0 ±4.95 



2 3382 61.0 ±4.58 



3 2135 60.7 ±4.46 



4 1099 60.2 ±4.56 



5 or higher .... 1672 59.4 ±4.14 



These data confirm the observation of workers with other breeds that the first 

 egg of the clutch is likely to be the heaviest and that as the clutch size increases, 

 the mean egg weight declines at a slower rate. The data also furnish evidence 

 that eggs laid in very large clutches throughout the year are less variable in weight 

 than those laid in smaller clutches. 



Inherited Variability in Egg Weight 



The correlation between mothers and daughters in March variability in egg 

 weight may be used as an estimation of inherited variability. The standard 

 deviation in March egg weight was calculated for each family of three or more 

 daughters. These values were paired against the March variability in egg 

 weight of the respective dams. The following constants appeared: 



