At 14d, 21d and 28d the antibody titer of NDV were determined and the relative weight (%BW) of thymus, spleen and bursa were estimated.

• 测定了14、21、28日龄时各组试验鸡血清中NDV抗体水平及胸腺(thymus) 、脾脏(spleen)和法氏囊(bursa)免疫器官指数;