L-carnitine improves developmental competence of buffalo oocytes in vitro

Objective: To investigate the effect of L-carnitine on in vitro maturation and subsequent in vitro embryo production of buffalo oocytes. Methods: Cumulus oocyte complexes (COCs) were aspirated from ovaries of slaughtered buffaloes. COCs were classified into good and fair qualities based on morphological observation of numbers and integrity of cumulus cells surrounding the oocyte. Both categories of COCs were placed in in vitro maturation medium with supplementation of different concentrations (0, 0.250, 0.375 or 0.500 mg/mL) of L-carnitine. Oocytes from both qualities were in vitro fertilized and in vitro cultured for 7 days, to examine the developmental competence. Results: Supplementation of L-carnitine to in vitro maturation medium increased the cumulus cell expansion rate of COCs to grade A, and reduced the cumulus cell expansion of COCs to grade B and grade C in both good and fair quality oocytes. Similarly, L-carnitine induced the in vitro meiotic progression of buffalo oocytes to metaphaseⅡ in both good and fair quality oocytes. Additionally, L-carnitine reduced the rate of oocyte degeneration in both good and fair quality oocytes. L-carnitine increased the rate of cleaved formation at day 2 and blastocyst formation at day 7 during in vitro culture in both qualities of oocytes. Moreover, a higher rate of blastocyst production was observed in L-carnitine-treated fair quality oocytes, which was higher than the results in the untreated good quality oocytes. Conclusions: L-carnitine enhances meiotic maturation and subsequent embryo development from both good and fair quality buffalo oocytes.