Development and quality of sheep embryos cultured in commercial G1.3/G2.3 sequential media

Abstract

Present study assesses the developmental ability and quality of ovine IVP embryos derived from culture in sequential media G1.3/G2.3. A total of 1474 cumulus–oocyte complexes were matured in M199 supplemented with EGF and FCS for 24 h in 5% CO 2 in humidified air at 39 °C. Oocytes were co-incubated in SOF medium with 1 × 10 6 spermatozoa/ml at the same temperature and gas conditions (Day 0 p.i.). Presumptive zygotes at 20 h p.i. were denuded, washed and placed in culture in SOF (control; n = 742) or G1.3 media supplemented with 3 mg/ml of BSA ( n = 732) under mineral oil in a humidified and controlled atmosphere at 39 °C. Embryos in the treated group were changed to G2.3 medium on Day 3 of culture. A group of blastocysts in each group were frozen by conventional method (SOF, n = 55; G1.3/G2.3, n = 48). In vivo embryos ( n = 72) were recovered at Day 7 from the uterus of progestagen + eCG treated females and they were cultured in defined medium ( n = 38) or frozen ( n = 34) directly after recovery. Cleavage rate of IVP embryos recorded at 48 h p.i. was similar for control and treated embryos (49.8 versus 47.5%). There were no significant differences in blastocyst development from the two groups on Day 6 (26.0 versus 25.6%), 7 (42.1 versus 38.6%) or 8 (50.8 versus 43.2%). Blastocyst development rates from total oocytes cultured were comparable (24.1 versus 21.5%). However, the proportion of hatched blastocysts was significantly higher for control embryos (86.6 versus 44.3%, P < 0.0001). In addition, embryos cultured in SOF had higher re-expansion rates post-thawing at 24 h (38.2 versus 6.2%), 48 h (36.4 versus 4.1%) and 72 h (34.5 versus 4.1%) and hatching rate (32.8 versus 2.0%) than embryos cultured in sequential media ( P < 0.0001). In vivo embryos showed higher hatching rate (61.7%) than IVP groups (SOF, P < 0.01; G1.3/G2.3, P < 0.0001) but lower than their fresh cultured counterparts (86.8%; P = 0.01). In conclusion, G1.3/G2.3 media supported high developmental rates of embryos in vitro but the quality of the embryos was impaired.