6 MASS. EXPERIMENT STATION BULLETIN 344 



PART I. EGG WEIGHT 



A. Winter Egg Weight 



Winter egg weight as used in these studies is the mean of all eggs laid from 

 the first pullet egg to January first of the first laying year. Such information 

 is valuable particularly in the selection of pullets for breeding purposes. The 

 three lines of birds will be considered separately in this report. 



Chart 1 indicates the general trend with respect to winter egg weight in the 

 three lines. The mean winter egg weight showed a gradual upward trend 

 throughout the experimental period in all three lines, which was much more 

 pronounced in lines B and C. From 1930 to 1935 the daughters in line A had 

 a heavier mean egg weight than their dams. This fact suggests that the sires 

 of these daughters must have transmitted greater egg size than the dams. On 

 the other hand, in lines B and C the daughters for the most part fell below 

 their dams in egg size. It is probable that the inheritance for egg size of the 

 sires used was not equal to that of the dams. The data show a general parallel- 

 ism in egg weight between mothers and daughters. 



The mean egg weight of all the daughters to January first was as follows: 



Line A, 52.23 ± .143 grams (22.1 ounces to the dozen) 

 Line B, 53.81 ± .168 grams (22.8 ounces to the dozen) 

 Line C, 53.85 + .169 grams (22.8 ounces to the dozen) 



The difference between the means for lines A and B was 1.58 ± .221 grams, 

 which is definitely significant. The difference between the means for lines B 

 and C was .04 ± .238 grams, which is insignificant. Evidently the plan of 

 breeding followed was effective in producing heavier egg weight in line B than 

 in line A, but not effective in producing greater egg weight in line C than in 

 line B. 



Correlation between Winter Egg Weight and Hatching-Season Egg Weight by Lines 

 For market purposes and in the production of eggs to be used for hatching 

 later in the season, certain weights are desirable. Information relative to the 

 association between egg weight up to January 1 and egg weight in February 

 or March following should be helpful to the breeder. 



The populations in the three lines were tested for normalcy in winter egg 

 weight. In all three lines the probability of a normal sample was very high. 

 The X 2 test for normalcy in hatching-season egg weight also showed all three 

 lines to be satisfactory samples. 



The regression of hatching-season egg weight on egg weight to January 1 

 was strictly linear in all three lines. The coefficients of correlation were as 

 follows: 



Line A, + .7211 ± .0211 



Line B, + .8131 ± .0141 



Line C, + .8556 + .0118 



These are very significant constants and indicate that about 65 percent of the 

 variation in hatching-season egg weight is associated with variation up to 

 January 1. The data show further, from the regression coefficient, that on the 

 average pullets that lay 53-gram eggs (22.5 ounces to the dozen) up to January 

 1 may be expected to lay 56.7-gram eggs (24 ounces to the dozen) in February 

 and March. 



