Abstract: Effective control of mastitis in dairy cows and the balanced regulation of their rumen flora are key to maintaining stable lactation performance and maximising production value. In dairy farming, frequent occurrence of mastitis is often caused by multiple bacterial infections, which not only seriously affects the lactation performance of cows, but also directly leads to a decline in milk quality. It has become common practice to use large quantities of antibiotics to deal with mastitis. However, while this strategy can provide temporary relief, it poses the challenge of increased bacterial resistance, which greatly reduces the effectiveness of subsequent treatments. Worse still, the use of broad-spectrum antibiotics can also accidentally kill beneficial flora, especially in the rumen, affecting the overall health and nutrient absorption of the dairy cow.As a virus that can specifically recognize and kill bacteria,phage has the characteristics of high killing efficiency,high specificity,no drug residues and other green and efficient features.Therefore,this paper provided a comprehensive overview of the concepts, mechanisms of action with bacteria, effects on lactation performance of dairy cows, and advantages and disadvantages of phage therapeutic modalities. The aim is to provide a theoretical basis for the application of phage therapeutic methods in dairy farming and to promote green development.

Key words: phage, bacteria, dairy cow, lactation