The potential of oocytes based on the status of ovary activity to achieve the level of in vitro maturation in Bali cattle

Abstract

Abstract The physiological condition of slaughterhouse bovine ovaries may vary greatly, including the luteal phase, follicular phase, and pre-puberty. However detailed information is scarce on how it affects oocyte maturity in vitro. Therefore, this work aimed to investigate the impacts of ovarian activities on the oocyte maturity of Bali cattle in vitro. Completely randomized designed was arranged, consisting of three ovarian stages (luteal, follicular, and pre-cycle) as a research variable and carried out at four replication. Oocytes were recovered by slicing the follicles from surface-visible ovaries. The oocyte maturation was performed in an incubator containing 5% CO2 at 38.5°C. Following the removal of the cumulus, the oocyte was prepared for fixation, then observed under a microscope. The research showed that the structure of oocyte grades A (compact cumulus cells and thick cytoplasm) in the follicular and luteal phase was similar, but such condition was significantly different compared to the prepubertal phase. The oocyte maturity of M-II was significantly lower (P<0.05) in the pre-cycle phase than in the luteal and follicular phase. Meanwhile, the stages of GV, GVBD, and MI appeared to be identical in all phases. This work concluded that the structure of the oocyte population is closely related to ovarian stages, resulting in higher maturity on M-II oocytes during the luteal and follicular phases.