In vitro embryo culture using sequential media to alter carbohydrate availability has been shown to improve embryo development. Further, upregulation of embryo lipid metabolism using L-carnitine has been shown to improve blastocyst development and quality. This study aimed to examine the effect of temporal upregulation of lipid metabolism in a sequential media system on embryo development and quality.
Oocytes were matured for 44h and subjected to IVF using frozen-thawed boar sperm. Presumptive zygotes were cultured in PZM31 with modifications, and assessed for cleavage rates on d3, and blastocyst development and cell number on d7. After the optimal dose of L-carnitine was determined, embryos were cultured with PZM3 supplemented with 3mM L-carnitine for either d0-7, d0-3, d4-7, or without L-carnitine for d0-7. Finally, embryos were cultured in standard PZM3 for d0-7 or with a change to modified PZM3 (0mM pyruvate, 0mM lactate, 5.55mM glucose) for d4-7, and with or without 3mM L-carnitine for d0-3 of culture. Cleavage and blastocyst data were analysed by ANOVA and Tukey’s post-hoc test. Cell count data was analysed by Student’s T-test.
The addition of 3mM L-carnitine to the culture media increased rates of cleavage (81%) relative to the control (66%; P<0.05). Blastocyst development rate was decreased with the addition of 6mM L-carnitine (6% vs control 17%; P<0.05). There was no difference in blastocyst rates or cell numbers when 3mM L-carnitine was added temporally to culture media (P>0.05). Use of sequential media did not increase blastocyst development rates (P>0.05), although blastocyst cell numbers were increased in all sequential media groups compared to standard PZM3 culture (P<0.05).
Upregulating lipid metabolism during early embryo culture improved cleavage rates, although not blastocyst development. These findings indicate that sequential media with changing substrate concentrations in conjunction with L-carnitine may better meet the metabolic requirements of early porcine embryos.