• Energy Research

Most systems for producing mammalian embryos in vitro use glucose as an energy source despite putative toxic effects. It is known that female embryos are more sensitive to negative effects of glucose during IVC. The aim of this work was to evaluate whether replacing glucose with myo-inositol and citrate during IVC affects sex ratio. 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. The percentages of blastocysts were recorded and the embryos (on average 122 per group) were sexed by PCR as previously described (Alomar, 2008, Anim. Reprod. Sci. 107 48-61.). Differences in blastocyst rates and in the percentages of female embryos between groups were analyzed by Chi-Square test. The results of this study showed that myo-inositol-citrate increased both blastocyst yield (37.4 vs 29.5 %, respectively; P<0.01) and the percentage of female embryos compared to glucose (61.5 vs 45.6 % respectively; P<0.05). In conclusion, these results suggest to use myo-inositol and citrate in culture media to switch embryo sex ratio towards females.

The aim of this work was to evaluate whether minimizing the glucose concentration during culture or replacing the hexose with other energy substrates and/or embryotrophic compounds would affect the in vitro development, the resistance to cryopreservation and the sex ratio of bovine embryos. In vitro matured and fertilized oocytes were randomly assigned to 4 groups for in vitro culture, that differed in the energy substrates included: group A) 1.5 mM glucose, as in standard SOF; group B) 0.15 mM glucose; group C) 0.125 mM G3P, in the presence of 0.15 mM glucose and group D) 0.34 mM citrate, in combination with 2.77 mM myo-inositol. Blastocysts were evaluated on day 7, then vitrified by cryotop in 16.5% DMSO, 16.5% EG and 0.5 M sucrose and warmed in decreasing concentration of sucrose (0.25 to 0.15 M sucrose). The survival rates were assessed after 24 h in vitro culture. Finally, the blastocysts produced were sexed by PCR. An increased blastocyst rate was recorded in groups B, C and D, i.e., when glucose concentration was reduced, compared to group A (28.2, 41.0, 35.7 and 35.8, respectively in groups A, B, C and D; P < 0.01). However, the embryos cultured in group D showed the slowest developmental speed, indicated by the lowest percentage of advanced stage-embryos (expanded and hatched blastocysts) out of the total blastocysts (56.1, 45.8, 56.9 and 31.8 %, respectively in groups A, B, C and D; P < 0.01). Furthermore, survival rates after 24 h culture of vitrified-warmed blastocysts also decreased in group D (73.3, 73.1, 71.4 and 58.4%, respectively in groups A, B, C and D; P < 0.01). Interestingly, in group D a higher percentage of female embryos was obtained compared to group A, with intermediate values in groups B and C (45.6, 53.4, 50.0 and 61.5%, respectively in groups A, B, C and D; P < 0.05). In conclusion, it was demonstrated that the energy substrate during in vitro culture affects both the production and the viability of blastocysts. Furthermore, manipulating the metabolic profile of embryos during in vitro culture may have an impact on sex ratio.