Direct and Maternal Genetics With Environmental Effect for Egg Quality and Hatchability of Gimmizah Chickens Selected for Body Weight

Abstract

The present experiment was conducted on Gimmizah (GM) chickens selected for body weight at 12-wk of age through three generations aiming for detection the genetic components of direct, maternal and environmental effects of egg quality traits and hatchability. Second generation of GM chickens selected for body weight represent increase (p>0.05) of some egg quality traits such as hatching egg weight, egg shape index, egg surface area, egg shell density, eggshell thickness without membranes, albumen weight, albumen height, yolk weight, and egg shell weight compared with those for base population (G 0 ) and first generation (G 1 ). Generally, Additive genetic maternal was surpassed those for the additive genetic direct and permanent environmental hen effects for the most studied traits. Realized heritability estimates among the three selected generations proved that the records of direct estimate (h 2 a ) had highest value of heritability compared with those for maternal (h 2 m ) and permanent environmental hen effect (h 2 pe ) with respect to hens body weigh at 45-wk of age, hatching egg weight, egg surface area, eggshell thickness without membranes, albumen weight, albumen height, yolk weight ratio, eggshell weight, eggshell weight percent, albumen weight percent, and yolk/albumen ratio. Also, highly significant positive genetic correlations are detected between most of the studied egg quality traits and hatchability. Also, there are highly maternal positive maternal genetic correlations between hatching egg weight and each of egg shape index, eggshell thickness, albumen weight, albumen height, yolk weight, fertility, total embryonic mortality and hatchability of fertile eggs. The obtained results of low estimates of heritability for fertility and hatchability and the highly estimates for egg quality traits besides the highly direct and maternal genetic correlations suggesting the applicability of some egg quality traits in programming the selection index combining with body weight selection as indirect way for improving fertility and hatchability with body weight.