A study of the genetic variability of egg quality traits for developing effective improvement programs
Keywords:
Backcross generations, no dominance,, parental strains, additive genetic variance, egg quality, egg weight.Abstract
External and internal egg quality traits are the primary selection objectives of breeders to maximize the
return of saleable eggs. In order to help for developing an effective improvement program for egg
quality traits, performances of F3 and backcrosses generations, derived from crossing Gimmizah with
Bandarah developed strains, were used to estimate the components of genetic variability of egg quality
traits in this experiment. The current results revealed that the differences between genetic groups were
highly significant for all traits studied. Also the variations between F3 and backcrosses were highly
significant differences for egg weight, shell weight, yolk weight, albumin weight and yolk index, while
shell thickness, egg shape index and Haugh unit were not differ significantly in the same trend.
Moreover, the results revealed that most of egg quality characteristics had negative estimates of
additive ⌠²A and dominance σ²d genetic variations. This may be due to the parental strains were closely
related, what caused presence of many deleterious recessive genes, were expressed largely and
resulted a very little genetic variations in egg quality traits. The degree of dominance (ĥ) was varied
from no dominance in shell weight to complete dominance of the low parent in yolk index and from
complete dominance of the high parent in albumin weight and egg weight to over dominance of the low
parent in Haugh unit. Contrarily, over dominance of the high parent was found in shell thickness, egg
shape index and yolk weight, respectively.