Antibiotic pretreatment minimizes dietary effects on reconstructure of rumen fluid and mucosal microbiota in goats.

We used 16S rRNA gene sequencing to examine the posteffects of antibiotic treatment on the structure and metabolism of rumen microbiota. Twelve goats were randomly assigned into two groups, with one group receiving intramuscular streptomycin injection at 40 mg/kg bodyweight daily for 10 days. At 4 weeks after treatment with antibiotic, three goats were randomly selected from each group and switched to a 35% concentrate diet. The remaining six goats continued with the 10% concentrate diet. At 4 weeks after dietary shift, ruminal fluid and epithelium were collected to analyze the microbiota composition and short-chain fatty acid (SCFA) concentrations of the rumen. We found that antibiotic administration led to increases in the diversity and richness of recovered mucosal microbiota and to decreases in those of recovered fluid microbiota. When dietary modulation was performed after antibiotic intake, both communities showed little difference in structure from premodulated states. Additionally, antibiotic pretreatment reduced the basal lines of individual SCFAs but did not affect the increased percentages of SCFAs. Overall, our results indicate that antibiotic administration affects the structure of both rumen fluid and mucosal microbiota and reduces the functional redundancy of rumen microbiota.