Development of porcine oocytes from preovulatory follicles of different sizes after maturation in media supplemented with follicular fluids

The development of porcine oocytes from large (3.1-8.0 mm in diameter) or s mall (<3.1 mm) follicles was examined after maturation culture in medium co ntaining porcine follicular fluid (pFF). Large follicles yielded larger (25 6 <mu>m v. 221 mum; P<0.05) cumulus-oocyte complexes and more (22 v. 14%) m orphologically normal oocytes than small follicles (Experiment 1). In Exper iments 2-4, maturation media supplemented with mixed pFF (10%) from small a nd large follicles was used. More oocytes from large follicles matured (58% v. 91%), formed pronuclei (81% v. 90%) and developed to the blastocyst sta ge (2% v. 10%) than oocytes from small follicles. In Experiments 5-7, the e ffects of pFF collected from either small or large follicles on oocyte deve lopment were examined. Regardless of the source of oocytes, large-follicle- derived pFF more significantly enhanced preimplantation development than di d small-follicle-derived pFF. The highest rate of blastocyst formation (16% ) was found when oocytes from large follicles were cultured in maturation m edium containing large-follicle-derived pFF. These results suggest that ooc ytes from large follicles have greater developmental potential than oocytes from small follicles, and that the origin of pFF, which is added to the ma turation media, might be an important factor for improving in vitro develop ment of porcine oocytes.