6 MASS. EXPERIMENT STATION BULLETIN 384 



the incubation period. This fact furnishes rather definite evidence that the 

 early emerging chicks are the more viable. 



Table 3. — Number of Chicks and Percentage Mortality by Emergent 



Periods 



Emergent Period 



Number of Chicks 15 166 970 1,978 1,151 355 126 



Percent Mortality First Eight Weel<s 

 Sex Unknown: 



1st week .60 .72 1.06 .70 2.25 4.76 



Between 1 and 4 weeks .. . 2.42 2.08 2.20 1.40 3.46 2.50 



Between 4 and 8 weeks .. . 0.00 1.06 1.93 2.66 5.37 4.27 



Date unknown 0.00 1.61 1.44 1.37 1.89 4.46 



Total 3.01 5.36 6.47 5.99 12.39 15.08 



Percent Mortality Between Eight and Twelve Weeks 



Males .76 .35 1.24 



Females .36 1.08 1.28 



Both Sexes .55 .68 1.26 



Percent Mortality from Twelve Weeks to Housing (Six Monfh.s) 



Males 0.00 3.45 3.32 1.57 3.13 8.33 



Females 3.13 1.79 2.84 3.03 1.35 4.76 



Both Sexes 1.90 2.59 3.11 2.18 2.35 7.02 



Total Mortality to 6 Months 4.91 8.50 10.26 9.43 14 74 22.10 



Relation of Length of Incubation Period to Laying-House Mortality 



A portion of the pullets produced was placed in the laying houses at about six 

 months of age and trapnested for 365 days. No culling was done and the mor- 

 tality rate from all causes was calculated for birds emerging during the different 

 periods. The summarized data are presented in table 4. 



The data indicate no relation between the time of emergence and mortality 

 rate in females between the ages of six and eighteen months. It appears, therefore, 

 that the length of the incubation period cannot be considered a criterion of future 

 viability in the laying house. 



Relation of Length of Incubation Period to Characters Affecting 

 Egg Production and to Winter and Annual Egg Production 



In the selection of pullets to be placed in the laying houses it is desirable to 

 make use of every possible criterion of egg-laying ability. It was therefore con- 

 sidered advisable to test the relationship between the length of the incubation 

 period in female chicks and certain fecundity traits, as well as winter and annual 

 egg production. 



