12 MASS. EXPERIMENT STATION BULLETIN No. 289 



SUMMARY 



Three lines were established, each on a different selection basis: Line A, 

 for uniformity in inherited characters affecting fecundity; Line B, for uniformity 

 of annual egg records; and Line C, for high annual records. Each line was carried 

 through four generations to study variability of inherited characters affecting 

 fecundity and the effect of some environmental influences upon variability in 

 egg production. 



Age at se.xual maturity shows a coefficient of variation of about 10 per cent 

 produced by environment in birds of the same genetic constitution for sexual 

 maturity. 



Winter intensity is highly variable in a flock, due to genetic differences. In 

 this experiment the variability was greatly reduced by selection of breeders in 

 four generations. There is no evidence to indicate that environment influences 

 clutch size. 



Winter pause duration may be reduced by constant selection and is also 

 greatly affected by environmental influences. 



There is evidence that degree of broodiness measured by total days broody 

 may be influenced by hereditary modifiers. 



Persistency shows a variation of about 10 per cent that may be ascribed to 

 environmental influences. 



Variability in winter egg production decreased only in Line C, and increased 

 inbreeding in successive generations did not reduce the variation in winter egg 

 records. 



Variation in annual egg records was less in Lines B and C than in Line A. 



Differences in hatching dates are responsible for about 7 per cent of the varia- 

 tion in annual egg records. 



Neither increase nor decrease in body weight of the pullets during the laying 

 year affected the annual egg records. 



House temperature near the freezing point reduces egg production; house 

 temperatures above 70 to 75° may perceptibly reduce production; and produc- 

 tion changes are likely to follow soon after temperature changes. 



REFERENCES 



Goodale, H. D., Ruby Sanborn and D. White, 1920. Broodiness in Domestic 



Fowl. Mass. Agr. Ex-p. Sta. Bui. 199. 

 Graham, J. C, 1930. The Relation of Temperature to Egg Production. Proc. 



Poult. Sci. pp. 48-51. 

 Smith, C. W., 1930. The Relation of Environmental Conditions in Poultry 



Houses to Winter Egg Production. Neb. Agr. Exp. Sta. Bui. 247. 



3M 12-'32 No. 7088 



