Effect of addition of L-carnitine to the culture media on cryopreservation of bovine embryos produced in vitro

The in vitro production (IVP) of bovine embryos is increasing worldwide. However, it is known that IVP embryos are very particularly sensitive to slow freezing. Among the reasons for this; There are reasons such as embryos formed from abnormal oocytes, high cytoplasm lipid content, different lipid droplet arrangement, high reactive oxygen species (ROS) levels and low inner cell mass. It is reported that Lcarnitine is an antioxidant by reducing the amount of ROS and lipids and protecting cells from DNA damage. L-carnitine is thought to improve cryotolerance and developmental ability in IVP embryos, with its cellular lipid content lowering and antioxidant effect. The aim of this thesis was to investigate the effect of adding Lcarnitine to a culture medium on the survival and development rates of embryos during culture and after cryopreservation. The study material consisted of 508 ovaries collected from slaughtered animals. IVP embryos were produced from the collected A and B quality oocytes. The cleavage rates on the 3rd day of culture and the embryo development on the 6th day were evaluated. Six different groups were formed from embryos reaching the early blastocyst and blastocyst stage. L-carnitine-containing groups contained 0.75 mM L-carnitine. The culture process was continued without any treatment on the embryos in the control and LK-IVK groups. Embryos in Group YD and Group LK-YD were slow frozen, and embryos in Group VIT and Group LK-VIT were vitrified. Frozen embryos were kept in liquid nitrogen for at least one day and thawed. After the embryos were thawed, their development was observed for 3 days. In the evaluation of the culture on the 3rd and 6th days, the addition of L-carnitine to the culture medium did not effect cleavage and embryo development (p>0.05). When the control and Group LK-IVK were examined, it was determined that the addition of L-carnitine to the culture medium did effect the expanded blastocyst and hatching blastocyst rates at the end of the 24th and 72nd hours (p>0.05). However, at the 48th hour examination, the hatching rates of Group LK were found to be lower than those of Group Control (p<0.05). L-carnitine did not effect expanded blastocyst and hatching blastocyst rates at 24, 48 and 72 hours after thawing in slowly frozen and vitrified embryos (p>0.05). As a result; It was determined that the addition of L-carnitine to the culture medium of IVP embryos did not affect the cleavage and embryo development rates at the 3rd and 6th days of culture, and the survival and development rates of vitrification and slow-frozen embryos. It is recommended to repeat the study with more numbers in future studies. If commercial medium is to be used in studies, the antioxidant content and density of the medium used must be known. It is recommended to measure lipid contents and ROS levels in evaluating the efficacy of L-carnitine in embryos.