经调查分析发现，造成免疫失败的主要原因是雏鸡母源抗体水平低。
The main causes of immunity failure were discovered that lower mother's antibody of chick by investigating and analysing.
灭活苗可以中和剩余的母源抗体，或更易于激活机体免疫力的产生。
It is felt the killed vaccine either neutralize the remaining maternal antibody or just more easily starts the development of immunity.
本试验用V_4株、V_4株和克隆- 30株联合苗对高母源抗体的雏鸡进行了口服、滴鼻与同居感染免疫试验。
Chicks of highly maternal antibody were tested with vaccines of V4 strain and V4 clone-30 strain by oral administration, nasal drip and cohabitation.
大多数的父母代鸡群经过了IBD活苗和灭活油苗的免疫，以产生高水平的母源抗体对3-4周龄的雏鸡提供保护。
Most parent flocks are vaccinated with both live vaccines and killed oil-emulsion products which produce a high level of maternal antibody that protects the chick for its first 3-4 weeks of life.
大多数的父母代鸡群经过了IBD活苗和灭活油苗的免疫，以产生高水平的母源抗体对3-4周龄的雏鸡提供保护。
Most parent flocks are vaccinated with both live vaccines and killed oil-emulsion products which produce a high level of maternal antibody that protects the chick for its first 3-4 weeks of life.
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