CORRELATED RESPONSE FOR EGG QUALITY TRAITS AFTER THREE GENERATIONS OF SELECTION FOR EGG NUMBER IN BENHA CHICKENS

The current study investigated the effect of selection for increased egg number during the 1 st 90 days of laying on egg quality traits over four generations in Benha chickens. A total of 18 cockerels and 180 pullets were selected according to their BLUP values for egg number at the first 90 days of laying from Benha base population (control). Data of 4242 eggs produced by 756 pedigreed hens fathered by 69 sires and mothered 484 dams from four generations (base and three selected generations) were used to estimate heritability, genetic and phenotypic correlations for egg quality traits (Egg weight (EW), Albumen weight (AW),Yolk weight (YW), Shell weight (SW), Haugh unit (HU), Egg shape index (ESI), Albumen index (AI), Yolk index (YI) and Egg shell thickness (EST)). The selection effects, correlated responses and the genetic and phenotypic trends for egg quality traits across generations were quantified or clarified applying the updated approach of the animal model program of BLUPF90. Heritability estimates were moderate or low for all traits (h 2 = 0.05 to 0.47). Also, genetic correlations for EW was closely positively genetically correlated with AW, YW, SW, with magnitudes of 0.99, 0.57, 0.69, respectively. The three selected generations were superior (P <0.05) in most egg quality traits than the base generation and the contrasts among estimates of these generations were significant (P<0.05). The phenotypic and genetic trend increased for all egg quality traits. While genetic trend decreased for AW. The accumulative correlated selection responses were 1.18 g for EW, 0.31g for SW, 5.27 for HU, and 0.06 mm for EST. Conclusion, these findings stated superiorities of selected generations indicating selection for egg number during the first 90 days of laying in Benha chickens was associated with an improvement in egg quality traits.