Morbidity for CRD of commercial broilers flocks were largely related to conditions of their houses, so environmentally controlled houses were better than those simple in regard to preventing CRD.

• 商品代肉鸡CRD的群患病率与鸡舍的环境条件有很大关系,标准化鸡舍在CRD的控制明显好于大棚鸡舍;