Superovulation treatment of immature female rabbits increases the number of ovulated oocytes that can in vitro develop into blastocytes

To clarify the efficiency of superovulation in immature female rabbits, immature female rabbits were superovulated with pregnant mare serum gonadotropin, and the number of recovered oocytes, their maturity, and their ability to develop into blastocysts under in vitro fertilization and culture were examined in this study. More than 80 oocytes were recovered from 12–14-week-old immature female rabbits. In particular, an average of more than 100 oocytes were recovered from 13-week-old immature female rabbits. The number of oocytes in immature female rabbits was significantly—approximately 4 times—higher than in mature female rabbits. To compare oocyte maturity, oocytes from immature and mature female rabbits were compared by brilliant cresyl blue staining and mitochondrial distribution analysis. The proportion of mature oocytes detected by brilliant cresyl blue staining was higher in oocytes from mature female rabbits than in oocytes from immature female rabbits, but there were no significant differences in active mitochondrial distribution, fertilization rate, or blastocyst development rate. These results indicate that superovulation with immature female rabbits may be a useful technique for the collection of many oocytes. •The efficiency of superovulation is higher in immature rabbits than mature rabbits•PMSG-treated immature and mature rabbits had similar oocyte sizes and cytoplasm•Higher numbers of oocytes were obtained from PMSG-treated immature rabbits•Oocyte cytoplasmic maturation was reduced in PMSG-treated immature rabbits•Fertilization and blastocyst development rates were normal in immature oocytes