10 MASS. EXPERIMENT STATION BULLETIN 384 



Body Weight at the End of the First Laying Year 



Heavy body weight at the end of the first laying year is important, according 

 to Hays (1939). It serves as a general measure of how well each individual has 

 survived a year of heavy laying. As a rule, those birds which fail to increase 

 in body weight and those which actually decline in weight will give unsatisfactory 

 hatching records the following spring as well as low egg records during the second 

 year. In table 9 mean body weights at the end of the first laying year, at about 

 eighteen months of age, are recorded for each emergent group. The absolute 

 weight of a bird at this time may be used as something of a criterion of the bird's 

 future value for breeding as well as for egg production. 



Differences in mean weight between the emergent groups were small and 

 bear no particular relationship to the time of emergence. It seems likely, there- 

 fore, that the length of the incubation period has no relation to body weight at 

 the end of the first laying year. 



Table 9. — Relation of Length of Incubation Period to Body 

 Weight at End of First Laying Year 



Emergent Number Mean Weight 



Period of Birds Pounds 



Evidence on Inheritance of Length of Incubation Period 



Since a large series of matings to test for possible inherited factors affecting 

 length of incubation period has not been made, some evidence on this point may 

 be gained from a study of the correlation between sires and sons and sires and 

 daughters as well as between dams and sons and dams and daughters in length 

 of incubation period. The constants arrived at from available data are given 

 in table 10. 



Table 10. — Correlations 



