Effect of folic acid addition to the medium on in vitro maturation of bovine oocytes

The effect of addition of different concentrations of folic acid (vitamin B9) to the culture medium on in vitro maturation of bovine oocytes was investigated in two experiments. Optimization of bovine oocyte maturation medium is one of the strategies affecting quality of maturity and fertility, ultimately resulting in increasing the quality of produced bovine embryos. In the 1st experiment, to specify the concentrations of folic acid and homocysteine, ovarian follicles were divided into two categories including follicles with more or less than eight mm of diameter. Then, the concentrations were measured in both follicle groups as well as a commercial culture medium. In the second experiment, bovine ovaries were transferred to the laboratory immediately after slaughter and the cumulus-oocyte complexes were collected by aspiration from 2-8 mm diameter follicles. Oocytes were randomly divided into four groups and different levels of folic acid (0, 10, 100 and 1000 ng/ml) were added to maturation medium based on the results of the first experiment. Following incubation of oocytes, the percentage of mature oocytes was determined by Hoechst staining. The concentrations of folic acid and homocysteine in follicles with diameter of less than eight mm was higher than those with diameter of greater than eight mm, as well as the culture medium Supplementation of maturation medium with 100 ng/ml folic acid increased the percentage of metaphase-II oocytes compared to the control (P <0.05). Considering the concentrations of folic acid and homocysteine in the medium, results showed that the addition of folic acid improves in vitro maturation of bovine oocytes.