EFFECT OF RECOVERY METHOD ON YIELD OF BOVINE OOCYTES PER OVARY AND THEIR DEVELOPMENTAL COMPETENCE AFTER MATURATION, FERTILIZATION AND CULTURE IN-VITRO

An important aim of an oocyte recovery method is to maximize the numbe r of oocytes per ovary which can be employed for in vitro maturation ( IVM), in vitro fertilization (IVF) and in vitro culture (IVC). In this study, primary bovine oocytes were collected by 2 methods: aspiration of visible follicles (2 to 6mm in diameter) or surface dissection in which the ovary surface is finely dissected. The oocytes were classifi ed on the basis of cumulus cover and cytoplasmic appearance. The total number of oocytes and the yield of good-quality oocytes recovered per ovary by surface dissection and aspiration were 44.2 and 13.9 and 13. 5 and 4.6 (P<0.05), respectively. When a sample group of selected oocy tes recovered by each method was measured, no significant difference w as found in the mean diameter (144.11mum vs 142.54mum). A representati ve sample of good-quality oocytes recovered by each method was put thr ough the IVM/IVF/IVC procedure: no significant difference in cleavage rate, cleavage index or blastocyst yield was found. However, when the blastocyst yield was compared on a per ovary basis a significant diffe rence was observed in favor of surface dissection (3.30+/-0.46 vs 0.96 +/-0.16;P<0.05). When unselected oocytes recovered by surface dissecti on of the ovaries were put through the standard embryo production syst em, an average of 15.4 blastocysts per dam was obtained.