Abstract: The objective of this study was to investigate the effect of cowherb seed extract on serum biochemical indexes,lactation related hormones and immune function of mid-lactating dairy cows.32 Chinese Holstein cows in parity 2 to 4 with similar weight and milk yield were selected and randomly divided into four groups and eight cows per group.Dairy cows were fed the diets supplemented with 0(control group),5.7 g/(head·d) (low dosage group),19 g/(head·d)(medium dosage group) and 38 g/(head·d) (high dosage group) cowherb seed extract.The pre-test lasted for 7 days,and the trial period lasted for 35 days.The results showed that compared with control group,the serum TP and ALB contents of each dosage group had no obvious change (P>0.05).The serum GLU content of each dosage group had a rising trend on the 30th day,while the serum TG and BUN contents of each dosage group had a decreasing trend,but the differences were not significant (P>0.05).Compared with control group,the serum PRL and GH contents of each dosage group increased at a certain degree,the medium and high dosage groups were significantly increased on the 30th day (P>0.05).Compared with control group,the serum IgA and IgG contents of each dosage group had a rising trend,while the serum IgM content of each dosage group had a decreasing trend,but the differences were not significant (P>0.05).In conclusion,dietary supplementation of cowherb seed extract could improve the energy metabolism and protein utilization,promote the lipid metabolism and increase the milk production of dairy cows.And the optimum supplemental level of cowherb seed extract in the diet of mid-lactating dairy cows was 19 to 38 g/(head·d).

Key words: cowherb seed extract; mid-lactation; PRL; GH; Holstein cow