Embryonic Mortality in Chicken Eggs as Influenced by Egg Weight and Inbreeding

The influence of egg weight (average between 41 and 60 weeks) and of inbreeding of the embryo on viability of the embryos was investigated with two lines of large egg weight (L1, L2) and their reciprocal crosses to a small egg weight population (L × BC, BC × L). Average egg weights of breeder hens for L1, L2, L × BC, and BC × L were 69.0, 74.5, 53.4, and 70.7 g, respectively. Inbreeding of embryos was 23.8 and 25.3% for L1 and L2 and ~0 for the other two groups. The different late embryonic death rates of the groups, i.e., 14.0, 23.6, 5.0, and 17.6%, could be explained by the different egg weights. Extent of inbreeding was not important for embryonic viability in the extreme egg weight range considered.