Energy source during in vitro culture (IVC) and sex ratio of bovine embryos

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.