الفهرس 
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Abstract
<U+2022> Introduction: Local strain of chicken suffer from many problems, such as hatchability reduction and increased embryonic mortality which resulted in decreasing the net return of poultry production. <U+2022> Aim of the study: This study was carried out to: (1) investigate the effects of hatchability season, vit. C concentration in dipping solution as well as the dipping period on egg weight loss, embryonic mortality, hatchability and chick weights up to 6 weeks of age. (2) to investigate the effects of hatchability season, injection dose of vit. C/egg and the injection day during incubation on the previously mentioned traits. <U+2022> Materials and Methods: Four experiments were carried out during Spring and Summer. Concentrations of vit. C in dipping solutions were 0.0 and 10.0 g/l distilled water for 1 or 2 minutes before incubation in the first and second experiments. However, in the third and fourth experiment the eggs were injected in air cell by 0.0, 3.0, 4.0 or 5.0 mg/egg vitamin C at 7, 9, 11, 13 or 15 days of incubation. A total of number 2020 egg were used in this study obtained from Sinai layers at 30 weeks of age. <U+2022> Results: Results showed that treating eggs with vitamin C by dipping or injection resulted in decreasing embryonic mortality, improving hatchability percent and chicks weight up to 6 weeks of age. <U+2022> Recommendations: It can be recommended to apply the dipping of hatching eggs in AA solutions (10.0 g/l) for 1 minute for small and mediumsized hatcheries. However, in the large modern hatcheries of, the automatic inovoinjection machine can be used in AA injection as 3.04.0 mg/egg in the 13th or the 15th day of incubation in order to get satisfactory results of hatchability, embryonic mortality and chick growth performance after hatch.