8 MASS. EXPERIMENT STATION BULLETIN 423 



The time required to attain standard egg weight was extremely variable. 

 The mean period was about fifty days, which we believe to be about normal for a 

 high-producing flock carrying the inheritance for large egg size. Regression was 

 not linear, and the correlation ratio .2111 indicates that the time required to 

 attain standard egg weight does affect annual egg production in a positive manner. 



14. Relation Between March Egg Weight and Annual Production 



Hays (1944b) showed that egg weight during the month of March is one of the 

 most valuable measures of egg weight that may be employed. Results of in- 

 vestigations of the relation of egg weight to number of eggs laid are not entirely 

 consistent. It is conceivable, therefore, that egg size may be one of the factors 

 that affect annual egg production. The following constants were calculated: 



Number of birds 612 



Mean March egg weight — grams 60.54 



March egg weight standard deviation ±3.95 



Mean annual production — eggs 213.67 



Annual production standard deviation ±42.29 



Coefficient of correlation -.0048 ± .0273 



Correlation ratio .1707 



March egg- weight records were available on 612 females and showed a mean 

 of 60.54 grams (25.7 ounces to the dozen). This mean showed that the birds 

 carried genes for large egg size even though a considerable proportion lacked 

 genetic purity. Regression of annual production on March egg weight was not 

 linear. The correlation ratio .1707 measures the association, which is negative. 

 In other words, heavy egg weight in March has a significant tendency to be 

 accompanied by fewer eggs for the first laying year. 



15. Relation of Annual Egg Weight to Annual Production 



This relationship has already been reported for the same population in Bulletin 

 416 (Hays, 1944). In this study regression was non-linear and the correlation 

 ratio between annual egg weight and annual egg production was .2297. This 

 constant was of a positive order, indicating that annual egg weight and annual 

 production tended to increase together. 



In general, time required to attain standard egg weight, mean March egg 

 weight, and annual egg weight all have significant effects on annual egg produc- 

 tion. Although these relations are not intimate, they must be considered in a 

 program of breeding to increase egg production. 



Body Weight 



16. Relation Between Body Weight at the End of the First Laying Year and 

 Annual Production 



Individual body weights were taken when the birds in the house had been 

 laying for about twelve months. It is desirable to know whether body weight 

 at that time showed any association with previous annual egg production. The 

 following constants were calculated: 



Number of birds 1340 



Mean body weight at end of year — pounds. . . 5.97 



Body weight standard deviation ± .77 



Mean annual production— eggs 214.31 



Annual production standard deviation ±43.30 



Coefficient of correlation -.0486 ±.0184 



Correlation ratio .2183 



