16S rRNA gene sequencing and analysis
Fresh fecal samples were collected and bacteria’s 16S rRNA gene sequence was detected using paired-end configuration on an Illumina MiSeq system (Illumina, San Diego, USA). Briefly, microbial DNA was extracted and DNA quality was examined by agarose gel electrophoresis. The V3-V4 regions of the bacteria’s 16S rRNA gene were amplified by PCR. The sequencing was performed using paired-end configuration on an Illumina MiSeq system (Illumina, San Diego, USA). Raw fastq files were demultiplexed, and then data was filtered to ensure quality. The taxonomy of each 16S rRNA gene sequence was analyzed by RDP Classifier (