| Abstract |
Prior to study, 17 breeds or strains were screened according to their performance, then ten genotypes of them were chosen to meet all levels of production based on their glutathione peroxidase (GSH-Px) at 56 days of age and two genotypes were chosen showing the highest Rhode Island Red (RIR) and the lowest enzyme activities (Gimmizah).A crossbreeding experiment was carried out between two genotypes of chickens namely RIR as standard foreign breeds and Gimmizah as developed strains. Two crosses were made: RIR x Gimmizah and its reciprocal cross (Gimmizah x RIR dams) to study crossing effects on variance components of the studied traits with an approach to potence ratio. The studied traits were GSH-Px , body weight (BW) at one, 28; 56, 84, 112 days of age, 5% and peak of egg production., egg production related traits (age at sexual maturity, ASM, egg number, EN, rate of lay, RL, egg weight, EW and egg mass, EM) and fitness traits.
Samples were taken at previous mentioned ages. Results showed that RIR had higher GSH-PX28, GSH-PX56, GSH-PX84, BW84, BW5%, EN180, EM90 and EM180 than other genotypes. Whereas, Gimmizah had higher GSH-Px1, GSH-Px5%, EN90, hatchability% and mortality than other groups. RIR x Gimmizah and its reciprocal had lower GSH-PX56 , GSH-PX84 , EN90, EN180. EM90, EM180 hatchability and mortality% than their parents. Estimates of direct additive effect were positive and significant for GSH-PX56 and GSH-PX84. BW5%, ASM, EN90, EN180, egg weight (EW), EM90 and EM180. However, a significantly negative direct additive for GSH-Px1 and GSH-Px5% and BW112 were found. All estimates of maternal effects were negative and significant for GSH-Px28 and GSH-Px5%, EN90, EN180, EW, EM90, EM180, Similar trend of negative maternal effect was found for each of fertility, hatchability, except BW112. Estimates of heterotic effect were significant for most studied traits. Heterosis was negative and significant for each of GSH-Px1, GSH-Px28, GSH-Px56 GSH-Px84 and GSH-Px5%, BW84, EN90, EN180, EM90, EM180, fertility, hatchability and mortality. On the other hand, heterosis% was positive and significant for each of BW1, BW112, ASM and EW. Estimates of PR showed that over-dominance for the dominant high parent (RIR) of GSH-Px5% BW56, EN90, RL, EW, fertility, hatchability, mortality. There were over-dominance effects for the low parent (Gimmizah) of GSH-Px28, GSH-Px56, GSH-Px84 and GSH-Pxpeak, BW1, BW84, BWpeak, ASM, EN180, EM180, abnormal chicks%.
In conclusion, RIR was favored as a sire for GSH-Px56, GSH-Px84, BW5%, and most egg production- related traits studied than Gim.
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