Abstract: In order to control mastitis,clinical mastitis pathogenic bacterial species of three dairy farms in different areas were isolated and identified.The types and infection condition of pathogenic bacteria,environmental conditions and management methods of the farms were analyzed.61 clinical mastitis milk samples from three different large-scale dairy farms in Fujian,Xinjiang,and Chongqing were collected for bacterial isolation and identification using traditional microbial identification methods and PCR technology.Among clinical mastitis milk samples collected in this trial,single infection sample was 44 (72.13%)and mixed infections sample was 15 (24.59%).80 bacteria were isolated,mainly E.coli,Staphylococcus and Streptococcus,including 13 strains of infectious microorganisms (16.25%),46 strains of environmental microorganisms (57.50%),11 strains of chance of microorganisms (13.75%),10 strains of other microorganisms (12.50%).Clinical mastitis in three dairy farms were still given priority to single infection,and mixed infection occupies certain proportion,with infectious pathogens and environmental pathogens as the main pathogenic.In the actual production the dairy cow mastitis infection and pathogen species could be carried out through the isolation and identification of mastitis pathogens in large-scale dairy farms.It was helpful to identify the herd management problems and make improvements to better control the occurrence of mastitis combining with the actual production conditions.

Key words: dairy cows; clinical mastitis; bacterial identification; species analysis