The effect of addition alpha tocopherol antioxidant on slow freezing medium to the quality of Garut sheep oocyte (Ovis aries)

Abstract

This study has evaluated the ability of alpha tocopherol antioxidant in maintaining the quality of Garut sheep oocytes post-cryopreservation using slow freezing method. Total of 226 oocytes with two different qualities (A and B) are matured in vitro in TCM-199 medium added with 150 µM alpha tocopherol. Afterwards, the oocytes were cryopreserved in the slow freezing medium with the addition of 0 µM (KK), 100 µM (KP1), 150 µM (KP2) and 200 µM (KP3) alpha tocopherol. Combination of cryoprotectant 10 % ethylene glycol (EG) and 0.1 M sucrose were also added to the medium slow freezing. Oocyte evaluation was carried out after 7 days of storage in liquid nitrogen (-196 °C), including oocyte morphology and oocyte viability using Hoechst and Propidium Iodide (PI) dyes. Based on the results of the study, the percentage of normal oocyte post-cryopreservation are 0 µM (67.86 %), 100 µM (68.42 %), 150 µM (74.58 %) and 200 µM (61.11 %). The percentage of viable oocyte post-cryopreservation are 0 µM (76.79 %), 100 µM (80.70 %), 150 µM (86.44 %), and 200 µM (70.37 %). The results shows that the addition of alpha tocopherol did not have an effect to the quality of oocytes post-cryopreservation, but there was a tendency for quality improvement with increasing doses of alpha tocopherol. In this study, addition of 150 µM alpha tocopherol into slow freezing medium is the best dose for maintaining the quality of Garut sheep oocytes until post-cryopreservation, although not significant (P > 0.05).