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.