The Effect of L-Carnitine Supplementation in Culture Medium on the Development and Cryopreservation of in Vitro Produced Bovine Embryos

Abstract

Background: In vitro culture media play a crucial role in supporting the growth and development of bovine embryos. Despite advancements in media formulations, there is ongoing interest in optimising these media by supplementing them with compounds like L-carnitine to improve embryo development and cryopreservation outcomes. However, the effects of L-carnitine supplementation in commercial culture media remain unclear. The aim of this study was to investigate the effects of adding 0.75 mM L-carnitine to commercial in vitro culture (IVC) media on bovine in vitro embryo production (IVP). The first phase of the study evaluated the effects of L-carnitine on embryo development, while the second phase evaluated the effects of L-carnitine on embryo cryopreservation. Methods: A total of 508 bovine ovaries used in the study were harvested from slaughterhouses. Only morphologically healthy ovaries were included in the study, while ovaries with cysts or any pathological findings were excluded. Oocytes were collected by aspiration method. The collected oocytes were fertilised in vitro using prepared spermatozoa under standard conditions. Following fertilisation, embryos were morphologically evaluated, and only those exhibiting uniform blastomeres and minimal cytoplasmic fragmentation were included in subsequent steps. The embryos were then randomly divided into two groups: one supplemented with 0.75 mM L-carnitine in the IVC medium and the other without supplementation. Cleavage rates on Day 4 and embryo development rates on 7 days after fertilisation were evaluated with the supplementation of L-carnitine. In addition, the survival effects of embryos collected on Day 7 after direct culture, slow freezing and vitrification were investigated. Results: It was determined that L-carnitine supplementation to IVC medium did not affect the cleavage rates on Day 4 and blastocyst development rates on Day 7 (p > 0.05). Moreover, it did not affect the survival and development rates of embryos collected on Day 7 following both slow freezing and thawing, as well as vitrification and warming processes (p > 0.05). Conclusions: Supplementation of L-carnitine to commercially available in vitro culture medium did not enhance embryo development rates or survival rates after cryopreservation. This is likely due to the presence of antioxidant compounds in commercial embryo culture media.