Effects of L-Carnitine on the Developmental Competence of Bovine Oocytes

The in vitro production of embryos has significant potential to enhance animal productivity. However, further refining of this technology is required for its widespread adoption and cost-effectiveness. The objectives were to evaluate the effects of L-carnitine (LC) on the maturation, lipid content, and Hippo signaling of oocytes, and the cryotolerance of the resulting embryos. Abattoir-derived oocytes were in vitro matured using fetal bovine serum (FBS), bovine serum albumin (BSA), or FBS + 1.5 or 3.0 mM LC. The maturation rates did not differ among FBS (83%) and FBS with LC (1.5 or 3.0 mM; 82 and 80%, respectively). In contrast, the BSA group exhibited a significantly lower maturation rate of 71% compared to the other groups. The lipid content of matured oocytes (assessed using Nile red staining) was significantly reduced in the BSA group and in the FBS + LC groups, compared to the FBS group. The blastocyst-stage embryos were cryopreserved, and their cryotolerance was evaluated by assessing their ability to re-expand and hatch after thawing. The embryos from the FBS + LC groups showed a numerically higher re-expansion rate at 24 h (78.8%), compared to the BSA (74.0%) and FBS groups (57.7%). The expression of Hippo signaling pathway genes was not significantly affected by LC, indicating that LC enhanced cryotolerance and reduced lipid content without impacting oocyte maturation or the Hippo signaling pathway.