Résumé
The present work aimed to study the effect of seasonal variations on the recovery rate, quality of recovered oocytes and maturation rate of buffalo oocytes in vitro. The effect of culture period on maturation rate was studied. The follicular oocytes were collected from ovarian follicles [2-5 mm in diameter] of slaughtered buffaloes by aspiration method. The recovered oocytes were classified morphologically into three categories [A, B and C]. The selected recovered oocytes [class A and B] were matured in tissue culture medium-199 supplemented with 10% fetal calf serum and antibiotics at 39°C, 5% Co[2] and high humidity for two different culture periods [21-24 hr and 25-28 hr]. Cultured oocytes were examined for nuclear maturation. The results indicated that, the average number of buffalo oocytes was 3.33 +/- 0.81 oocytes /ovary, without significant variation between the four, seasons. A higher [p<0.001] percentage of high quality oocytes was obtained in winter, autumn, spring than the summer season, while the percentage of poor quality oocyte [class C] was increased significantly [p<0.01] during summer. Moreover, the percentage of oocyte suitable for maturation decreased in summer than other seasons. The maturation rate of oocytes cultured for 21-24 hr was lowered than that recorded after 25-28 hr incubation period, among different four seasons. It is concluded that the quality of buffalo oocytes but not the recovery rate was affected by the seasonal variations. Increasing in the time of culture period was associated with improving in maturation rate. The high quality oocytes and high maturation rate can be obtained all over the year except summer season after culturing for 25-28 hr in vitro