GENETIC-PARAMETERS OF SURVIVAL TO THE DIFFERENT STAGES OF EMBRYONIC DEATH IN LAYING HENS

Heritabilities and genetic correlations of fertility (FERT) as well. a s of susceptibilities to early (EEM), medium (MEM), and late (LEM) emb ryonic mortalities conditional on fertility and survival to earlier st age(s) of embryonic mortality were estimated with a general Linear mod el using a logistic link function on 59,794 eggs obtained from 6,480 h ens issued from 228 sires and 1,053 dams. Estimated heritabilities of FERT, EEM, MEM, and LEM were, when estimated from sire and dam compone nts, respectively, equal to 0.09 and 0.31, 0.09 and 0.25, 0.07 and 0.2 0, 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 PERT, E EM, MEM, and LEM were favorable with the exception of correlations bet ween FERT and MEM and between EEM and MEM when estimated from the sire component. These results show the theoretical interest of distinguish ing the three stages of mortality.