engleski

The influence of follicle size on the developmental kinetics of bovine embryos

The aim of the present study was to investigate the effect of follicle size from which oocytes originate on their subsequent ability to be fertilized and to undergo early embryonic development in vitro. Cumulus oocytes complexes (COCs) aspirated from small (≤ 5 mm) and large (> 5 mm) follicles of abattoir-derived ovaries were graded for their morphological appearance and were cultured to assess their developmental competence. In order to study the kinetics of early cleavage, the number of cleaved embryos was recorded at 24, 27, 30, 33, 36 and 48 hours post insemination (hpi). A rapid rise in the rate of cleaved embryos was observed by 27 hpi, for both oocytes collected from ≤5 mm and >5 mm follicles. However, oocytes recovered from follicles >5 mm cleaved in significantly higher proportion at 24 to 30 hpi, which was reflected to higher overall cleavage rate at 48 hpi. The kinetics of early cleavage was consistent with subsequent development of embryos, that is, the oocytes from >5 mm follicles which completed the first cell division faster developed to morula stage at Day 5 and blastocyst stage at Days 6 and 7 in higher proportion than oocytes from ≤5 mm follicles. Hatching rate on Day 9 was significantly higher when oocytes originate from follicles > 5 mm. Total cell number was not affected by follicle size. The results showed that oocytes derived from follicles > 5 mm display higher developmental competence than oocytes from ≤5 mm follicles, in terms of timing of first cleavage, timing of blastocyst development and overall blastocyst rate. The selection of oocytes based on follicle size and kinetics of cleavage could be useful tools in selecting the best embryos for transfer.

oocyte ; follicle size ; developmental competence ; cleavage ; cow

nije evidentirano