Study of Ovarian Follicular Development During Summer and Winter Seasons in River Buffalo

Buffalo is one of the farm animals with prominent economical importance and in Iran its population is in noticeablenumber. Twenty two pairs of buffalo ovaries were collected from slaughter houseduring summer and winter seasons and transported to histology laboratoiy within appropriate fixative. After paraffin embedded, semiserially sectioned and stained with HandE, histological and morphometerical investigations are carried out. Histological observation showed that a layer of cuboidal cells on the surface of ovary resting on the thick layer of connective tissue tunica albuginea and different types of ovarian follicles were embedded in loose connective tissue of the cortical stroma. By using a calibrated light microscopic lens device the follicle diameter was measured and data showed that the non-growing follicles had diameter of 26.4±.31 jam, on the other hand, the full grown follicles showed a diameter of 1905.7±279.8 jam. There were highly significant (P<0.01) differences in mean distribution of healthy and atretic follicles during summer, whereas this was only significant(P<0.05) during winter., During both seasons, number of atretic follicles is higher than healthy ones. Differences in mean distribution of healthy and atretic follicles during Summer was highly significant ( P<0.01) during the luteal phase and only significant (P<0.05) during the follicular phase. During winter difference was not significant. These results suggested that, during winter because of the reduced rate of follicular atresia, differences between healthy and atretic follicles is insignificant. Differences between mean distribution of healthy and atretic follicles in one year were highly significant (P<0.01). It is to be noted that the highest number of healthy follicles were noticed in winter, while the highest number of atretic follicles were seen in summer. The results of this study clearly showed seasonality of buffalo reproduction and ovarian activity. In conclusion, ovarian activity in summer because of hot stress is lower than in winter.