Effect of oxygen tension and serum during IVM on developmental competence of bovine oocytes

With an aim to improve the in vitro production of bovine embryos, the present study investigated the effect of serum and oxygen tension during IVM on oocyte developmental competence. Four experimental groups were evaluated: G1, 10% oestrus cow serum (OCS) with 20% O-2; G2, 0.1% polyvinyl alcohol (PVA) with 20% O-2; G3, 10% OCS with 5% O-2; and G4, 0.1% PVA with 5% O-2. The proportion of MII oocytes, blastocyst rates and total cell number were not affected (P > 0.05) when the OCS was replaced with PVA under 5% O-2, whereas a higher (P < 0.05) blastocyst rate and total cell number were found with OCS compared with PVA under 20% O-2. The apoptosis index was lower in blastocysts from oocytes matured with PVA under 5% O-2 (G4) compared with other groups (G1, G2 and G3), but no differences (P > 0.05) were found in maturation and blastocyst rates. Significant differences were found in the amount of specific transcripts in oocytes matured under different conditions. In conclusion maturation with PVA and 5% O-2 provides an efficient in vitro culture condition for the maturation of bovine oocytes.