A total of 720 Lohman brown parent-breeding layers were randomly divided into 4 dietary treatments .The basal diet were supplemented 0.05% terramycin,0.1% and 0.2% compound probiotics,respectively.

• 试验选用25周龄罗曼褐父母代蛋种鸡720只；随机分为4个组；试验组分别在空白对照组饲粮基础上添加0.；05%25土霉素、0