library_construction_protocol: Cecal tissues were collected and immediately frozen in liquid nitrogen, Microbial DNA was extracted from 200 mg of samples. The 16s RNA gene special regions were amplified by polymerase chain reaction, and the PCR products were analyzed and separated by electrophoresis. Afterwards, the 16S rRNA gene clone library was sequenced and analyzed using an Illumina NovaSeq 6000 platform.