الفهرس 
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Abstract
The recent experiment was carried out at the Poultry research farm of the Faculty of Agriculture, Menoufia University, Shebin El-Kom, Egypt, during the period from 2019 to 2022 for two generations aiming to improve some egg production traits by using selection indices in Norfa chickens. Data on 1078 Norfa hens including age at sexual maturity (ASM). body weight at sexual maturity (BWSM). egg weight at sexual maturity (EWSM) and egg number during the first 90 days of laying (EN90) were individually recorded. Data computerized and selection applied by selection index method helping appropriate statistical and genetic analysis software programs.
Results showed that, in the second generation of the study sexually matured earlier than the first by 12.17 days. In addition, either body weight or egg weight in the second and the first generation didn’t differ significantly in second and first generation. Application of selection index method resulted in improving average EN90 in the second generation compared with first generation by 2.5995 eggs (with high statistical importance). The highest value of h2 (heritability) recorded by body weight (0.231 and 0.197 for BWSM and BWM, respectively). Moreover, the lowest heritability estimates detected for EN90 (0.130) and EWM (0.117) in studied flock of Norfa chickens. Moderate to high estimates (0.255, 0.186 and 0.368) of h2 were observed for EN90, EWSM and ASM, respectively, in current study.
Results showed that using general index in selection for one generation resulted in improving egg production traits under investigation. The actual genetic gains for ASM, BWSM, BWM, EN90, EWSM, EWM and EN42 were -11.724 days, +52.88 g, +11.177 g, +2.5951 eggs, -1.1244 g, -0.391 g and +6.4637 eggs, respectively. It can be concluded that applying selection indices including the main egg-laying traits (i.e., EN42, EWM and BWM) leads to improve laying performance of Norfa hens regardless of the negative correlations detected between some traits at a multi-trait selection method.