BODY WEIGHT AND EGG PRODUCTION 13 



40 to 100 percent. Beginning with the class of birds weighing 5 pounds, there 

 was a consistent decline in mortality as weight increased. Mortality was about 

 30 percent for the group weighing from 5 to 5.24 pounds and fell well below 10 

 percent when weight was greater than 8.5 pounds. In this particular group of 

 birds it was necessary to have a mean weight of 7.5 pounds or more if subsequent 

 mortality was to be less than 15 percent. In other words, culling of small birds 

 at twelve months of age would appear to be an effective means of reducing summer 

 mortality. 



Relation between Body Weight and Egg Production 



10. Body Weight on March 1, and Annual Egg Production 



Mature body weight of the first laying year, taken about March 1, is probably 

 one of the best gross measures of adult size. Weight records and annual production 

 records are available on 1,338 birds from which the correlation between body 

 weight and annual egg production was determined. The following constants 

 were obtained: 



Number of birds 1338 



Mean body weight, pounds 6.62 



Weight standard deviation + . 75 



Mean annual production 213 .48 



Production standard deviation ±42 . 20 



Coefficient of correlation - . 1526+ .0180 



Correlation ratio 1901 



The data show that the birds were of a large strain and that the variation in 

 weight was not excessive. Annual egg production was high, with a rather wide 

 range of variability. 



The coefficient of correlation was of a negative oider, but regression was not 

 strictly linear so that the correlation ratio of . 1901 measures the true association. 

 There was a statistically significant negative correlation between body weight 

 and annual egg production. The squared value of the constant, however, showed 

 that less than 4 percent of the variation in annual egg production was associated 

 with variation in body weight. In this flock body weight was but remotely 

 associated with egg production. 



11. Increase or Decrease in Body Weight during the Laying Year, and Annual 



Egg Production 



A total of 1,309 birds with complete annual weight and production records 

 was again classified into three classes with respect to weight increase or decrease 

 from time of housing to the end of twelve months in the laying houses, and the 

 mean annual egg record of each class recorded. 



Table 6 shows that the group of birds gaining one-half pound during a year 

 in the laying houses laid a slightly greater number of eggs than any other group. 

 The eggs laid by this group of birds fell below a 24-ounce standard for the year. 

 On the basis of volume of egg material produced, the group gaining 1.5 pounds 

 was equal to the group gaining .5 pound, and egg size for the former was sat- 

 isfactory throughout the year. From the standpoint of number of eggs and size 

 of eggs, an increase in body weight of about 1.5 pounds during the first laying 

 year would seem to be desirable in this flock. 



