Growth and development of rabbit oocytes in vitro: Effect of fetal bovine serum concentration on culture medium

The objective was to develop a culture system that produced blastocyst stage embryos from rabbit oocytes grown in vitro. Two experiments were performed. First, various concentrations of fetal bovine serum (FBS, 0, 0.05, 0.5 and 5%) were used in the culture medium for in vitro growth (IVG) of oocytes recovered from follicles 200 to 299 μm in diameter. Intracytoplasmic sperm injection (ICSI) was performed on mature oocytes obtained after IVG for 8 days and in vitro maturation for 14 to 16 h. Rates of survival and pronuclear formation after ICSI were higher for oocytes grown in a medium with 0.05% FBS compared to oocytes grown in a medium lacking FBS (97.6 vs. 76.9%, 97.5 vs. 70%, P < 0.1). The rate of development to the blastocyst stage was also higher in the medium containing 0.05% FBS than in the medium lacking FBS (9.5 vs. 17.9%, P < 0.05). Next, using oocytes recovered from follicles 200 to 399 μm in diameter which were cultured in 0.05% FBS, oxygen consumption and the number of cells were analyzed. Blastocysts from oocytes grown in vitro with 0.05% FBS had reduced oxygen consumption and number of cells compared with those from ovulated oocytes (21.66 ± 4.54 × 10¹⁴ vs. 50.19 ± 4.61 × 10¹⁴ mol/sec, 244 ± 25 vs. 398 ± 24, P < 0.05). Rabbit oocytes grown in vitro with 0.05% FBS achieved pregnancy, but pregnancies were not maintained to term. In conclusion, the addition of 0.05% FBS to the culture medium for IVG improved developmental competence of rabbit oocytes grown in vitro.