Abstract
l-carnitine is a potent antioxidant used for in vitro culture systems. Controversial results have been reported using l-carnitine in culture medium at different stages of in vitro bovine embryo production. Cumulus-oocyte complexes (n = 843) were in vitro-fertilized and cultured and added (treatment group) or not added (control group) with l-carnitine. At day three of culture, each group was subdivided into two subgroups receiving no l-carnitine (group 1), 3.8 mM l-carnitine added during in vitro maturation (group 2), 1.5 mM added during the in vitro culture (group 3), and 3.8 mM and 1.5 mM added during the maturation and culture, respectively (group 4). At day 8, blastocyst embryos were examined for mitochondrial activity, the presence of lipid droplets, total cell number, gene expression, and cryotolerance by vitrification. The data were analyzed with a one-way analysis of variance. l-carnitine added in the late in vitro culture significantly reduced mitochondrial activity and lipid content, and upregulated ifn-τ and ptgs2 gene expression compared to controls (p < 0.05). l-carnitine supplementation did not significantly affect the embryo rate production or survival rate after vitrification and warming (p > 0.05). l-carnitine supplementation significantly improved embryo potential to develop viable pregnancies in agreement with a study reporting improved pregnancy rates.