Variance and covariance of hatchability and some of its components in the chicken¹

Part of a thesis submitted by the author to the University of London for the degree of Ph.D.

Synopsis

Samples of 20 hatching eggs from each of 2004 individual pedigreed pullets were incubated and hatchability recorded. Unhatched eggs were examined for evidence of embryo development and classified as infertile, early embryonic death (died 0–10 d) or late embryonic death (died 11–22 d). Variance analysis yielded a mean heritability value for hatch of all eggs of approximately 0.30. Heritability values for early and late embryo mortality were subject to larger errors but there was a tendency among the estimates of h ² ₈ for late embryo mortality to be higher than those for early embryo mortality.

The genetic correlations between hatchability and both early and late embryonic mortality were high and negative as was to be expected from part × whole correlations. However the genetic correlation between early and late embryonic mortality was also consistently positive indicating common genetic determination of these two independent traits.

Notes

Part of a thesis submitted by the author to the University of London for the degree of Ph.D.

Present address: Shaver Poultry Breeding Farms Ltd, Galt, Ontario, Canada