In order investigate the efficacy of immunopotentiator( VA5) on bivalent vaccine in chickens,the antibody levels or the challenge protection efficacy were evaluated after the specific pathogen free chickens( SPF) and commercial layers immunized with the bivalent inactivated ND-IBD vaccines with or without VA5,respectively. The other detection way was only taking SPF chicken injected by bivalent ND-AI vaccines with or without VA5,in contrast with bivalent vaccine without VA5 groups. HI antibody level against...