Effect of energy source on in vitro embryo development and freezability in cattle

Most media employed for producing bovine embryos in vitro include glucose as an energy source despite putative toxic effects. The aim of this work was to evaluate whether replacing glucose with myo-inositol and citrate during IVC improves in vitro embryo development and resistance to cryopreservation. Abattoir-derived oocytes were matured and fertilized in vitro using standard procedures. After 20–22 h of gametes co-incubation, zygotes were denuded and cultured in SOF containing either 1.5 mM glucose or 2.77 mM myo-inositol and 0.34 mM citrate for 7 days. Embryos were first incubated in 7.5 % EG and 7.5 % dimethyl sulfoxide (DMSO) for 3 min, then transferred into 16.5 % EG and 16.5 % DMSO and 0.5 M sucrose for 25 sec before being loaded into the cryotop. Warming was carried out by immerging the cryotop into a 0.25 M sucrose solution and by transferring the embryos into a 0.15 M sucrose for 5 min. Vitrified-warmed embryos were then cultured in vitro for further 24 hr, after which the embryo survival rate was recorded. Data were analyzed by Chi-Square test. The results of this study showed that myo-inositol-citrate increased blastocyst yield (37.4 vs 29.5 %, respectively; P<0.01). However, blastocysts produced in the medium containing myo-inositol and citrate had a lower survival rate after vitrification-warming than those cultured with glucose (60.4 % and 73.6 %, respectively; P<0.05). In conclusion, replacement of glucose with myo-inositol and citrate during culture increases blastocyst production without improving embryo quality, i.e. resistance to cryopreservation