Germinal vesicle stages in pig follicular oocytes collected by different methods

Abstract

In Exp. 1 oocytes were collected from follicles (4-6 mm) in ovaries from prepubertal gilts by aspiration of the follicles with a syringe or dissection from healthy follicles. After aspiration some oocytes with compact cumulus and granulosa cells were selected. In Exp.2 oocytes were collected from follicles (4 mm, 5-6 mm and 7-8 mm) of gilts on the 18th-19th day of the cycle. Germinal vesicle (GV) stages of oocytes were examined and categorized into GV1, GV2, GV3 and GV4. In Exp. 1 when collected by aspiration, a significantly lower percentage of oocytes (45%) was arrested at the GV1 stage than oocytes from dissected follicles (78%). However, after morphological selection of oocytes, the percentage (58%) significantly increased. In Exp 2, significantly higher percentages (86-90%) of oocytes from follicles of 5-8 mm in diameter were at the GV1 stage than oocytes from follicles in diameter of 4 mm (24%) and atretic follicles (57%). These results indicate that by aspiration some oocytes are collected from follicles that were inadequate to maintain arrest at GV1, but significantly higher percentages of oocytes at GV1 can be obtained after morphological selection of oocytes or isolation from large follicles of gilts on the 18th-19th day of the cycle.