IN-VITRO MATURATION OF POST-THAW VITRIFIED BOVINE IMMATURE OOCYTES

A total of 319 fresh bovine ovaries were obtained from the local abattoir. COCs were cryopreserved using a vitrification solution comprising TCM-199 (HEPES modified) with 10% FBS and two cryoprotectants of 20% ethylene glycol (EG) and 20% dimethyl sulfoxide (DMSO). Vitrified COCs were stored in liquid nitrogen (LN2) for 7 days and then thawed. Morphologically normal COCs were tested for in-vitro maturation to record morphological changes of COCs during vitrification. Freshly collected COCs were separately used for in-vitro maturation and kept as control. By aspiration method, 816 oocytes were recovered with an average of 2.72 ± 0.14 oocytes per ovary. The average recovery rate of grade A, B, and C oocytes were 8.67 ± 0.82, 5.77 ± 0.41 and 2.62 ± 0.31respectively. The proportions of COCs that were recovered in morphologically normal form following vitrification was 83.68% and the in-vitro maturation rate of vitrified COCs was 74.20 ± 1.88 % as compared to non vitrified control ( 87.09 ± 1.63 %). Vitrification of immature bovine oocytes using 10% EG + 10 % DMSO for equilibration and 20%EG + 20%DMSO with 0.6M sucrose as vitrification solution yielded acceptable in-vitro maturation rate.