Effect of Oocyte Maturation Period on Developmental Rate and Sex ratio Distribution of in vitro Produced Bovine Embryos

It has been suggested that the maturation status of the oocytes at the time of fertilization influences the sex ratio of resulting embryos produced in vitro. Therefore, the duration of the oocyte in vitro maturation is likely a simple method that leads to in vitro production of embryos with the desired sex. For this purpose, the current study was conducted to investigate the effect of in vitro maturation culture period of bovine oocytes on the sex ratio of resulting blastocysts. The abattoir ovary-derived oocytes were cultured for vari-ous duration of in vitro maturation (16 h, 20 h, 24 h, 28 h, and 36 h). After in vitro fertilization and culture of mature oocytes, nested multiplex polymerase chain reaction (PCR) with AMELX and SRY primers was used to determine the sex of blastocysts. The results of this study showed that the cleavage and blastocyst rates were increased by prolongation of in vitro maturation (IVM) duration from 16 hours to 24 hours and deceased from 24 hours to 36 hours (P<0.05). The sex ratio of male embryos in aged oocytes (36 hours IVM) was significantly higher than in other groups (P<0.05). In conclusion, the maturation duration of bo-vine COCs influences the sex distribution of embryos in the blastocyst stage appearing on day 8, and the male embryos were recovered more than female counterparts by increasing the oocytes culture period.