EFFECTS OF OOCYTE MATURATION MEDIA ON DEVELOPMENT OF PIG EMBRYOS PRODUCED BY IN-VITRO FERTILIZATION

Few embryos derived from pig oocytes matured and inseminated in vitro are able to develop to blastocysts in culture. The present study was c onducted to examine the effects of oocyte maturation media on the deve lopmental ability of pig oocytes matured and inseminated in vitro. Fol licular oocytes collected from ovaries of prepubertal gilts were cultu red in NCSU23 medium, tissue culture medium 199 or a modified Whitten' s medium. All of the media were supplemented with 0.57 mmol cysteine l (-1) and 10% pig follicular fluid. After maturation, some of the oocyt es were used for examination of intracellular glutathione content, nuc lear maturation and cortical granule distribution. The other oocytes w ere inseminated in vitro in a modified Tris-buffered medium with cryop reserved, ejaculated spermatozoa for examination of cortical reaction, sperm penetration, male pronuclear formation and blastocyst developme nt. No differences (P > 0.05) were observed in nuclear maturation, cor tical granule distribution, sperm penetration, male pronuclear formati on, polyspermy and cleavage in oocytes matured in the three media. How ever, significant (P < 0.05) differences were observed in glutathione content, cortical granule exocytosis, blastocyst development and numbe r of cells in blastocysts. NCSU23 medium gave the best results of the three media, resulting in 5.8 pmol glutathione per oocyte, 97% of cort ical granule exocytosis, 30% blastocyst development and 36.8 +/- 17.0 cells per blastocyst. These results clearly indicate that cytoplasmic maturation of pig oocytes was significantly affected by oocyte maturat ion media even in the presence of cysteine and pig follicular fluid. I n addition, it was demonstrated that a large proportion of pig oocytes can develop to blastocysts under in vitro conditions.