Bovine oocyte in vitro maturation rates depending on the presence of cumulus cell in the medium ( fresh and afther cryopreservation)

The obtained COCs from bovine ovaries were divided into groups and matured in vitro in a dropof IVM medium (Stroebech, Copenhagen, Denmark) with a volume of 100 μL under mineraloil. Groups: fresh immature COCs (immCOCs), fresh COCs after IVM (fCOCs), cryopreserved COCs after IVM (cryo-COCs), freshly denuded oocytes after IVM (fDOs), cryopreserved denuded oocytes afterIVM (cryoDOs), fresh denuded oocyte matured in vitro with a fresh suspension of CCs(fDOs + fCCs), cryopreserved oocytes matured in vitro with a cryopreserved suspensionof CCs (cryoDOs + cryoCCs), fresh CCs after culturing in IVM media (fCCs), cryopreservedcumulus cells after culturing in IVM media (cryoCCs). For co-culture, a suspension of CCs at a concentration of 5 × 105/mL was addedto the oocytes in a drop of the same volume. The maturation rate was estimated after 22 h by calculating the percentage of oocytes with an extrusion of the first polar body.The measurements of the maturation rate were repeated at least three timesin each group.