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

Improvements in culture media formulations have led to an increase in the ability of sheep embryo in culture throughout the preimplantation period. 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. 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. 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). It seems that addition of 1.5 of MEM vitamins has detrimental effect on blastocyst rate.