294 



MASS. EXPERIMENT STATION BULLETIN 258 



INBRED DAMS 

 CHECK GAliS 



— INBRED DXUOHTIRB 



— • — ' — '— CKECi: PAUQHTEF.S 



1923 



I'iZt 



1520 



1927 



1S2» 



1925 

 KITIHO YlAKfl 

 CHART 1. — Effect of Inbreeding on Sexual Maturity 



Chart 1 shows how age at sexual maturity behaved. The fact will be noted 

 that both inbred dams and check dams were of the same age, about 176 days, 

 at first egg in 1923. In 1924 the age for inbred dams increased to 186 days, 

 while the check dams increased to 197 days. In 1925 inbred dams were 193 days 

 old and check dams were 235 days old when they laid their first egg. The 

 daughters from the dams in the inbred group showed a mean age of 206 days in 

 1923, 208 days in 1924, and 204 days in 1925. Inbreeding apparently did not 

 affect the mean age of daughters. The check daughters of 1923 averaged 238 

 days; those of 1924, 254 days; and those of 1925, 189 days. Early sexual 

 maturity in the three check daughters for 1925 came from their sire, C 7984, 

 that came from the production-bred strain, and he transmitted the dominant 

 genes for early maturity to his daughters. 



During the last three years of the experiment, when the checks were inbred 

 and the inbred strains intercrossed, all dams and all daughters in both groups 

 averaged 200 days or less at first egg. This places them in the class of genetically 

 early maturing birds. On the whole, chart 1 does not indicate for this experiment 

 that inbreeding aiTected age at sexual maturity. 



INBRED DAifS 

 CHECK DAMS 



— INB.RED DAUGHTERS 



— ' — • — • - CHECK DAUGKTEHS 



1926 



1927 



1923 192'» 1925 



WATINO YEARS 

 CHART 2. — Effect of Inbreeding on Weight at First Egg. (Weight in Pounds) 



1924 



