Abstract: Abstract： The objective was to study effect of different antibiotic combinations on growth of rumen bacteria with a Hungate’s roll tube technique to isolate anaerobic fungi from rumen fluids of dairy cows. Penicillin, Streptomycin, Chloramphenicol and Metronidazole in different levels were added to 9.0 mL solid or liquid mediums prior to the anaerobic inoculation. Based on counting results of bacteria and fungi up to three day, the combination of 0.8 mg/mL Penicillin and 1.2 mg/mL Streptomycin did not inhibit the growth of rumen bacteria in mediums. However, the combination consisted of 0.8 to 1.2 mg/mL Penicillin, 1.2 to 1.8 mg/mL Streptomycin and 0.004 to 0.08 mg/mL Metronidazole significantly inhibited the growth of rumen bacteria without negative impact on that of anaerobic fungi (P<0.05). Similar inhibition also occurred for the combination consisted of 0.8 to 1.2 mg/mL Penicillin, 0.6 to 1.2 mg/mL Streptomycin, 0.1 to 0.3 mg/mL Chloramphenicol and 0.004 to 0.008 mg/mL Metronidazole. In general, antibiotic resistance of rumen bacteria should be paid more attention, and the combination of different antibiotics in this study might provide an alternative reference for the effective control of bacteria growth in the application of a roll tube technique to isolate anaerobic fungi from the rumen fluids. 

Key words: Key words：antibiotics; rumen; fungi; bacteria; anaerobic roll tube technique