BODY WEIGHT AND EGG PRODUCTION 9 



Number of birds 486 



Mean body weight, pounds 6.72 



Weight standard deviation ± . 80 



Mean annual egg weight, grams 58.59 (24.8 oz. per dozen) 



Egg weight standard deviation ±4.05 



Coefficient of correlation + . 3990 + . 0257 



Correlation ratio 4661 



The variability in body weight was not excessive, since it amounted to only 11 

 percent of the mean. The birds used may therefore be said to be reasonably 

 uniform in mature body weight. 



Egg weight for the year was 58.59 grams or 24.8 ounces to the dozen. Varia- 

 bility in egg weight was less than 7 percent, which indicates a high degree of 

 uniformity. 



Regression of egg weight on body weight was shown not to be strictly linear 

 by Blakeman's test. The coefficient of correlation between egg weight and body 

 weight was .3990 + .0257, and the correlation ratio was .4661. The magnitude of 

 these constants indicates that egg weight depends in considerable measure upon 

 body weight. Almost 22 percent of the variation in egg weight may be attributed 

 to variation in body weight. 



Relation between Body Weight and Persistency 



5. Body Weight at Housing, and Persistency 



The question arises as to whether pullets that are heavy in weight when housed 

 are likely to show greater persistency in laying than birds that are lighter in 

 weight when housed. The coefficient of correlation between weight at housing and 

 annual persistency will furnish some information. The following constants were 

 calculated: 



Number of birds 1513 



Mean weight at housing, pounds 5.16 



Housing weight standard deviation + . 60 



Mean annual persistency, days 334.46 



Persistency standard deviation +40.92 



Coefficient of correlation + . 1771 ± .0168 



Correlation ratio . 2454 



The birds averaged to weigh 5.16 pounds when housed and there was a range 

 in weight from 3.25 to 7.24 pounds. The coefficient of variation was almost 12 

 percent. Since this population includes birds from all experiments, there would 

 be a somewhat greater range in weight than would appear in birds bred for high 

 egg production. 



The mean persistency within the laying year was 334.46 days, with a range 

 from 82 to 366 days. The coefficient of variation in persistency was over 12 

 percent. It is evident that this somewhat mixed population was highly variable 

 in persistency. 



The coefficient of correlation between weight at housing and annual persis- 

 tency was .1771 ±.0168 but regression was not linear. The correlation ratio was 

 .2454 and indicates that about 6 percent of the variation in persistency was 

 associated with variation in weight at housing. This is not an intimate associa- 

 tion so that weight at housing cannot be considered an important criterion of 

 persistency in laying. 



