This study was done to evaluate susceptibility, protective titer level of maternal derived antibodies(MDAbs) of different chicken breed against virulent Infectious bursal disease virus (IBDV) local isolate Fy97 and prediction the optimal time for vacction. All breeds were experimentally infected orally with IBDV isolate Fy97 every 5 days following detection of MDAbs by ELISA. Clinical signs, mortality, lesions and Bursal Histopathology and lesion score were taken as criteria for comparison. Morbidity rates were observed as ≥ 30% in Fayoumi and Dandrawi infected at 15 days of age and in Senawi and Baladi and Lohmann at 20 days of age All breeds showed clinical sings of infection at 30-35 days of age where Senawi breed showed the highest values (65and 70%) followed by Fayoumi (55 and 55%), Dandrawi (50%), Baladi (55-45%) and Lohmann (50-45%). Mortality rates due to IBD infection varied from 0 to 35% in respective to age, in Fayoumi and Lohmann breeds where maximum 35 and 40% occurred at 30 day of age; respectively .Mortality in Dandrawi and Senawi varied from 5 to 40% and pass in close manner at all intervals with the highest value at 30 days of age while Baladi chicks showed same values but lower only at 20 and 25 days. Mean lesion scores in Fayoumi were the lowest at all intervals followed by Lohmann, Senawi, Baladi and Dandrawi. Results of ELISA titers at time of infection showed that Senawi chicks having the highest titers followed by Lohmann, Baladi, Dandrawi and Fayoumi at most intervals. So it necessitates more clarification of the causes of these phenomena and the role of genetics in protection against IBDV infection.