design: DNA extraction from the intestine samples was performed with the QIAamp Fast DNA Stool Minikit  extraction kit (Qiagen, Hilden, Germany), following the manufacturer's  protocol. The quality of the DNA samples from the microorganism community was  assessed by electrophoresis on 0.8% agarose gel and concentrations were  quantified in a spectrophotometer model NanoDrop ND-2000 (Thermo Fisher  Scientific, Wilmington, DE, USA). The libraries were prepared following the  Illumina recommendations. The hypervariable region V3-V4 of the 16S rRNA gene  was sequenced on a Illumina MiSeq, with v3 Reagent kit (Illumina, San Diego,  CA, USA) and the readings produced were 2x300 bp.