Abstract: To understand the effects of Chinese herbal medicine additives on milk yield, milk quality and subclinical mastitis of dairy cows in late lactation. 32 Simmental cattle with similar milk yield,body condition score,feed intake,parity and body weight were randomly selected in this experiment. The experiment was divided into 4 groups. On the basis of basic diet,0 g / head·d（control group）,100 g / head·d（low dose group）,200 g / head·d（medium dose group）and 300 g / head·d（high dose group）Chinese herbal medicine additives were added respectively. The pre-trial period was 3 days and the pilot period was 42 days. The results showed that there was no significant difference in milk yield between the low dose group and the control group after continuous feeding for 3 weeks. From the 4th week, the milk yield of the low,medium and high dose groups increased significantly,the milk yield in the 4th week increased by 6.90%,9.92% and 9.07% respectively（P<0.05）,the milk yield in the 5th week increased by 9.29%,13.27% and 11.17% respectively （P<0.05）,and the milk yield in the 6th week increased by 19.94%,27.25% and 25.56（P<0.05）,somatic cell counts decreased significantly by 37.77%,62.56% and 68.40%（P<0.05）,while the incidence rate of subclinical mastitis decreased by 33.33%,50% and 66.67%,but the milk protein rate and lactose content in the experimental group and the control group were not significantly different. The breast fat percentage in the high-dose group was significantly higher than that in the control group （P<0.05）. It was concluded that Chinese herbal medicine additives can slow down the rate of breast milk production,reduce the incidence rate of subclinical mastitis and improve the health of breast in late lactation,but have little effect on the change of milk quality.

Key words: Chinese herbal medicine additives, Simmental cattle, milk yield, milk quality, subclinical mastitis