Whole genome bisulfite sequencing of bovine oocytes from metabolically divergent lactating cows and nulliparous heifers

Lactating cows experience transient metabolic stresses during postpartum which results in abnormal concentrations of non-esterified fatty acids and beta-hydroxybutyrate that can impact oocyte maturation and ultimately reproductive success. We hypothesize that metabolic challenges in lactating cows influence DNA methylation changes of the oocyte affecting genes involved in oocyte developmental competency. Therefore, we compared whole genome bisultfite sequencing (wgbs) of the oocytes collected from 5-6 week (early) or 9-10 week (mid) post-partum against that of oocytes from nulliparous heifers as metabolically unchallenged condition control. Bisulfite-Seq DNA libraries were generated from pooled oocytes using an EZ DNA methylation-direct kit and Pico-Methyl seq library preparation kit (Zymo Research), and parallel sequenced using the illumina HiSeq2500 system.