300 



MASS. EXPERIMENT STATION BULLETIN 258 



per cent. These data do not indicate that inbreeding has any great influence on 

 the percentage of fertile eggs that hatch in those hens which actually produced 

 adult daughters. This point should not be confused with previous data show- 

 ing that under inbreeding more females fail to hatch any chicks. 



S 



/• 



\ 



/ 



/ 



/ 



1923 



1921+ 



IHBRED PROOENT 



• — I •- CHECK PROCEMT 



\ 



\. 



V 



\~ 



1926 



1927 



1928 



1925 

 KATISO TEiflS 

 CHART 9. — Effect of Inbreeding on Chick Mortality (Per Cent Mortality to Sept. 1) 



On chart 9 the mean mortality records by families for all progeny from hatch- 

 ing time to September first are presented. Inbred chicks showed a mortality 

 rate of 8 per cent in 1923, 19 per cent in 1924, and 50 per cent in 1925. The 

 chicks of the check group gave a mortality record of 25 per cent in 1923, 16 per 

 cent in 1924, and 17 per cent in 1925. These data show that the losses in the inbred 

 groups increased each year while the losses in the check group remained about 

 constant. If chick mortality is a measure of \'igor, inbreeding has reduced vigor. 



Crossing inbred lines in 1926, 1927 and 1928 has not consistently reduced chick 

 mortality. The mean records are 19, 31 and 20 per cent respectively. Inbreed- 

 ing the check groups has not significantly affected chick mortality. The figures 

 are as follows: 1926, 23 per cent; 1927, 34 per cent; and 1928, 8 per cent. The 

 mortaUty records for the two groups rather closely approach each other. As 

 a whole, these data signify that inbreeding did reduce chick vigor. 



100 



90 



- imRED D.WGHTEPJ 



I < — •- CHECZ Di'JOHTEaS 



70 



60 



\ 



to 

 30 

 20 

 10 

 



'\ 



\ 

 \ 

 \ 



\ ^ 



\ 

 '\ 



\ / 

 \ / 



\ 



1923 



192'+ 





1925 



UATINS YEAH3 



1926 



1927 



1928 



CHART 10. — Effect of Inbreeding on Laying House Mortality (Per Cent Mortality 



Laying House) 



