Genetic parameters of survival to the different stages of embryonic death in laying hens.

Heritabilities and genetic correlations of fertility (FERT) as well as of susceptibilities to early (EEM), medium (MEM), and late (LEM) embryonic mortalities conditional on fertility and survival to earlier stage(s) of embryonic mortality were estimated with a general linear model using a logistic link function on 59,794 eggs obtained from 6,480 hens issued from 228 sires and 1,053 dams. Estimated heritabilities of FERT, EEM, MEM, and LEM were, when estimated from sire and dam components, respectively, equal to 0.09 and 0.31, 0.09 and 0.25, 0.07 and 0.20, and 0.05 and 0.18; whereas estimated heritabilities of hatchability of fertile eggs were 0.05 and 0.15, respectively, when estimated from the sire or dam components. Most genetic correlations between FERT, EEM, MEM, and LEM were favorable with the exception of correlations between FERT and MEM and between EEM and MEM when estimated from the sire component. These results show the theoretical interest of distinguishing the three stages of mortality.