design: Sus scrofa ovarian mtDNAs were bisulfite treated by using Zymo EZ DNA Methylation-Gold Kit. Four regions (225 - 270bp) of mtDNA sequence were amplified from BS-treated DNA using bisulfite sequence primers designed by MethPrimer.   NGS libary was made from purified and pooled amplicons by Illumina TruSeq PCR-Free Library Prep kit and each NGS library was sequenced by Illumina MiSeq instrument using 150 bp paired-end sequencing chemistry.