Group I was the control , and other four groups ,groupII,III,IV,V were fed the diets containing 500,1 000,1 500,2 000 mg/kg of fluorine as sodium fluoride, respectively, for 150 days.

• 第 组 :正常对照组 , , , , 组在日粮中添加不同水平的氟化钠 ,使日粮中氟的含量分别为5 0 0 ,1 0 0 0 ,1 5 0 0和 2 0 0 0 mg/kg,试验期为1 5 0 d。