Current vaccination strategies for commercial poultry using live attenuated and inactivated Newcastle disease (ND) vaccines have some limitation and difficulties, and new vaccines with distinct features are needed. Recently, in ovo vaccination technology is concerned as a safe, efficacious, and convenient method. Common ND vaccines used in chickens cannot be employed in ovo due to embryo toxicity and high early mortality. One of the agents that may lead to attenuate ND virus (NDV) strains is aluminum hydroxide (AH) as an adjuvant. The objective of this study was to evaluate AH ability to attenuate NDV for in ovo administration of commercial pullets. Three hundred sixty fertile eggs of a Bovans strain as a factorial arrangement of six doses of the ND vaccine (50% egg infectious (EID50) of 0, 102, 103, 104, 105, and 106) with or without AH were ordered into 12 groups. At 18 d of incubation 0.1 mL of the inoculums was injected into the amniotic fluid of eggs. On the farm, each treatment group was further subdivided into two groups and one of these groups received ND-B1 vaccine on day seven posthatch. Lowest hatchability was recorded in groups vaccinated with doses of 105 and 106 EID50. On day 21, the highest hemagglutination inhibition (HI) was detected for group vaccinated with dose 102 EID50. Furthermore, hatchability and ND-HI titer were found to be up for pullets received AH in ovo on day 42 posthatch. The results of this study indicated that aluminum hydroxide as an adjuvant could significantly improve hatchability and immune efficacy of pullets when used in ovo. Further, lentogenic VG/GA strain-Avinew will have the potential for application as in ovo vaccine against Newcastle disease, if the vaccine is prepared with sufficient dose.

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