Effect of various concentrations of Minimal Essential Medium vitamins (MEM vitamins) on development of sheep oocytes during in-vitro maturation

Background: Improvements in culture media formulations have led to an increase in the ability of sheep embryo in culture throughout the preimplantation period. Objective: This study was carried out to evaluate the effects of various concentrations of MEM vitamins during in vitro maturation of sheep oocytes and subsequent embryo development. Materials and Methods: Sheep ovaries were collected from a slaughterhouse and transported to the laboratory. Oocytes were matured in SOF medium supplemented with, eCG, hCG and EGF in various concentrations of MEM vitamins (control, 0.5, 1 and 1.5 ) for 24h. The cumulus oocyte compelex (COCs) were co-incubated with epididymal spermatozoa of post mortem rams in synthetic oviduct fluid fertilization (SOFF) medium with 10% heat inactivated estrous sheep serum for 18h. Embryos were cultured in synthetic oviduct fluid culture 1 (SOFC1) medium for 48h followed by cultured in synthetic oviduct fluid culture 2 (SOFC2) medium for six days. Results: Addition of 0.5 and 1 MEM vitamins significantly increased (P< 0.05) overall blastocyst development (21.62% and 22.33%; respectively) compared with 1.5 MEM vitamins (15.59%), but there was no difference between control, 0.5 and 1 MEM vitamins in the percentage of embryos successfully developing to the blastocyst stage (19.50%, 21.62% and 22.33% respectively). Conclusion: It seems that addition of 1.5 of MEM vitamins has detrimental effect on blastocyst rate.