Distribution, morphometric evaluation and steroidogenic profile ofovarian follicles in cyclic and acyclic buffalo (Bubalus bubalis)

Acyclicity in buffaloes represents as one of the most prevalent disorders affecting fertility and productivity. It commonly occurs during the postpartum period or under conditions of nutritional, environmental, or metabolic stress, ultimately increasing the number of days open, veterinary interventions, and culling rates. Understanding the distribution pattern of follicles and their functional status is, therefore, essential for developing targeted reproductive interventions. The present study was conducted at ICAR-Indian Veterinary Research Institute, during 2021-22. Paired ovaries were collected from healthy adult buffaloes (n=75) at slaughter. Ovaries were classified as cyclic or acyclic based on the presence of a CL. Surface follicles were enumerated and categorized into small (<5 mm),medium (5–10 mm), and large (>10 mm). Follicular fluid from large follicles was aspirated for estimation of estradiol (E2), progesterone (P4), androstenedione (A4), and testosterone (T) concentration, and follicles were retrospectively classified as active (P4:E2 <1), intermediate (P4:E2 1–10), or atretic (P4:E2 >10). Acyclic buffaloes exhibited a greater proportion of ovaries with only small follicles (36.36%), compared with cyclic animals (9.43%), whereas only large follicles occurred predominantly in cyclic buffaloes. Cyclic buffalo ovaries also showed stage-dependent shifts in follicle distribution. Large follicles from cyclic and acyclic buffaloes displayed comparable steroidogenic patterns, with progressive increases in P4 and decreases in E2 from active to atretic categories. Further, the E2:A4 ratio was also significantly greater in the active follicle than in the atretic follicle. Thus, evaluating follicles using the E2:P4 and E2:A4 ratios provided a more accurate indication of follicular functional status than classification based solely on follicle size and cycle stage.