Microbial DNA was extracted from rumen samples using the HiPure Stool DNA Kit (Magen Biotechnology, Guangzhou, China). The V3-V4 region of the 16S rRNA gene was amplified by PCR with primers 341F (5'-CCTACGGGNGGCWGCAG-3') and 806R (5'-GGACTACHVGGGTATCTAAT-3'). Libraries were constructed and sequenced on the Illumina NovaSeq 6000 platform with paired-end 250 bp reads.