The relationship between ovarian follicle population and follicle size during different stages of estrous cycle in Anatolian Water buffaloes (Bubalus bubalis)

The objective of present study was designed to determine the relation of follicular growth patterns to stage of estrous cycle, using genital tracts from 137 Anatolian water buffaloes collected immediately after slaughter. The estrous cycle was classified as metestrous (days 1-4), early (days 5-10), and late diestrous (day 11-17) and follicular phase (days 18-21). The follicular population was counted and measured by water bath ultrasonography technique. The diameter of the follicles was divided into four stages: >= 12 mm; < 12 - >= 8 mm; < 8 - >= 5 mm and < 5 mm in diameter. Blood samples were taken for estimation of progesterone (P-4) and estradiol 17 beta (E 2) concentrations to confirm that buffaloes had normal ovarian function. The number of follicles < 5 mm in diameter showed no significant difference throughout the estrous cycle, whereas follicles between 5 and 8 mm in diameter were fewer during late diestrous and follicular phase. The number of follicles between 8-12 mm in diameter was less during metestrous and follicular phase. Follicles at least 12 mm in diameter were more numerous in follicular phase. During early and late diestrous, totally 87 animals had follicles larger than 8 mm (96.6%; 87/90) and only three animals did not show follicles larger than 8 mm, but they presented at least one large follicle during the following stage. These findings suggest that the majority of Anatolian water buffaloes develops two patterns of follicular wave.