Abstract: [Objective] To study the effects of dandelion extract on blood biochemical and immune indexes of dairy cows with persistent diarrhea.[Method] A total of 120 dairy cows with persistent diarrhea with similar weight,parity and average milk yield were selected as the study objects in a large-scale farm in Linshu County,and they were divided into 4 groups（n=30） by using random number table method,which were control group,experimental group 1,experimental group 2 and experimental group 3,respectively.Each experimental group was supplemented with 0.4%,0.6% and 0.8% dandelion extract under the basic diet,respectively.6 replicates were set in each group,with 5 dairy cows in each replicate.The pre-test period was 7 days,and the formal test period was 35 days.[Result] The BUN,TG and TC indexes of experimental groups were significantly lower than those of control group（P<0.05）,and the BUN,TG and TC indexes of test group 2 were the lowest（P<0.05）,but there was no significant difference between the other two groups（P>0.05）.The ALB index of experimental groups was significantly higher than that of control group（P<0.05）,and the ALB index of experimental group 2 was the highest（P<0.05）,but there was no significant difference between the other two groups（P>0.05）.The IgA and IL-2 indexes in experimental groups were significantly increased compared with control group（P<0.05）,and the IgA and IL-2 indexes in experimental group 2 were the highest（P<0.05）.The IL-4 index of experimental groups was higher than that of control group（P<0.05）,and there was no significant difference among the three experimental groups（P>0.05）.[Conclusion] Adding dandelion extract to the basic diet can improve the blood biochemical indexes and enhance the mune capacity of dairy cows with persistent diarrhea.Considering the experimental results，adding 0.6% dandelion extract to thebasic diet was the best.

Key words: dandelion extract, dairy cows with persistent diarrhea, blood biochemical index, immune index