Abstract
The present study was aimed to know the effects of L-carnitine on in vitro growth, embryo development and vitrification of buffalo oocytes. In 1st experiment, oocyte- granulosa cell complexes were dissected from early antral follicles of slaughtered buffaloes and cultured with the supplementation of different concentrations (0, 0.25, 0.375 and 0.5 mg/ml) of L-carnitine for 6 days. Further, in vitro grown oocytes were matured in in vitro maturation (IVM) medium for 24 hours. The results showed that L-carnitine enhanced oocyte growth in vitro. Significantly (p<0.05) lower numbers of oocytes degenerated in 0.5 mg/ml L-carnitine group than others. L-carnitine also enhanced the formation of antrum-like structures and nuclear maturation rate of in vitro grown buffalo oocytes. In 2nd experiment, cumulus-oocyte complexes (COCs) were aspirated from ovaries of slaughtered buffaloes and classified into good and fair qualities based on morphological observation. Both categories of COCS were placed in IVM medium with the supplementation of different concentrations (0, 0.25, 0.375 and 0.5 mg/ml) of L-carnitine. It was found that L-carnitine increased the cumulus cell expansion rate in both good and fair quality oocytes. Similarly, L-carnitine induced the in vitro meiotic progression of buffalo oocytes to MII in both categories. On the other hand L-carnitine reduced the rate of oocyte degeneration in both groups. To examine the developmental competence some of the oocytes from both qualities were fertilized in vitro and cultured for 7 days. L-carnitine treated oocytes showed increased rate of cleavage at day 2 and blastocyst formation at day 7 in both qualities. Moreover, a potential response of blastocyst production was observed in L-carnitine treated fair quality oocytes, which was higher than the results in untreated good quality oocytes. The results revealed that L-carnitine enhances meiotic maturation and subsequent embryo development from both good and fair quality buffalo oocytes. Aspirated COCS were screened and cryopreserved in vitrification medium supplemented with 0, 0.5, 1, 1.5 mg/ml L-carnitine in 3rd experiment. Recovery rate did not differ significantly in L-carnitine treated vitrified-warmed buffalo oocytes. Significantly higher percentage of survived oocytes and lower percentage of zona pellucida (ZP) and cytoplasmic anomalies were observed in 0.5 and 1 mg/ml L-carnitine groups than remaining ones. Moreover, significantly higher percentage of vitrified oocytes reached the MII stage in 0.5 mg/ml L-carnitine. Meanwhile, a lower percentage of degeneration was observed in 0.5 mg/ml L-carnitine treated group than the control. Thus, these experiments suggested that L-carnitine supplementation enhanced in vitro growth, nuclear maturation rates and embryonic development of both good and fair quality buffalo oocytes. L-carnitine also enhanced survival rates and developmental competence of vitrified oocytes. Therefore, it can be concluded from the present studies that the growth and developmental competence of buffalo oocytes could be increased through the supplementation of L-carnitine in vitro.