Methods: 150 14-day-old chickens were randomly assigned to 3 groups at 50 each. All groups were vaccinated with ND-IBD vaccine on 14th;

• 方法将150羽14日龄蛋公鸡随机分成3组,每组50羽,14日龄用一羽份新支二联弱毒苗点眼滴鼻免疫;