The objective of this experiment was to assess the features and extent of follicular apoptosis in the water buffalo (Bubalus bubalis) ovary using classical histology and nick end labelling technique. Ovaries (n=40) procured from the slaughterhouse were used for the study. The sections (5 μm) were used for detection of terminal deoxynucleotidyl transferase-mediated dUTP-biotin nick end labelling (TUNEL) and classical histology (H&E). Those follicles showing ≥ 5% TUNEL positivity (TUNEL assay) and pyknotic nuclei (histology) in granulosa cells were classified as atretic. Based on histology, the atretic primary and secondary follicles (%) were 93.82 and 95.62 respectively. The histology study reveals that the rates (%) of atresia in <1, 1-3, 3-5 mm and >5 mm were 36.90, 40.50, 62.84 and 74.5 respectively. Further the atretic tertiary follicles (%) were significantly lower than the primary and secondary classes of follicles. TUNEL assay reveals that the atretic rate (%) of tertiary follicles in <1, 1-3, 3-5 and ≥ 5 mm class follicles were 50.88, 53.84, 81.81 and 36.36 respectively. The percentage of atresia in >5 mm diameter follicles were significantly lower in TUNEL than histology. Percentages of granulosa and thecal cells positive for atresia by TUNEL were 30.7 ± 0.53 and 13.82 ± 0.18 respectively per follicle. The initial structural changes in atretic follicles were seen primarily in the granulosa cells. In severely atretic follicles TUNEL positive granulosa cells along with theca cells have to be considered in assessing the rate and extent of atresia.

The process of follicular development and features of morphological changes are essential to understand the factors involved during folliculogenesis and to improve fertility in buffalo. Hence the objective of the present study was to report ultrastructural features of atretic ovarian follicles in buffalo. In the early stage of atresia, the involvement of mitochondria was observed and whereas in the later stages of atresia, involvement of macrophages were observed. The granulosa cells of buffalo atretic tertiary follicles were observed to contain undulation of the nuclear membrane, crescent formation of the pyknotic nuclei and loopiness and undulations of the basal lamina. These features are similar to the reports in other species. The involvement of mitochondria in the early stage of atresia suggested the probable role of a reactive oxygen free radical induced damage.