Ovarian follicular dynamics in buffalo cows (Bubalus bubalis)

Abstract

Follicular growth in Egyptian buffalo cows was monitored using genital tracts from 200 buffalo cows collected immediately after slaughter. According to the morphological appearance of the corpus luteum (CL), the corresponding oestrous cycle was divided into four stages: A (days 1-4), B (days 5-10), C (days 11-17) and D (days 18-21). Within these stages the follicular population on the ovaries was evaluated and the dominant follicle (DF) determined in all recovered ovaries. The functional status of the DF and the largest sub-dominant follicles was examined by histological examination in 31 cases, and Radio Immunoassay (RIA) analyses for estradiol-17beta (E2) and progesterone (P4) was performed in the follicular fluid in 23 of the DF. The results showed that DFs changed their endocrine character within the stages of the oestrous cycle. The DFs between days 5 and 10 were functionally active (E2-dominant; non-atretic) in most of the cases. Between days 11 and day 17 half of the DFs became functionally inactive (P4-dominant; atretic). At days 18-21 all of the DF became functionally active and non-atretic. In the specimens that carried two large follicles one of them was regularly atretic and P4-dominant whereas the other was non-atretic and E2-dominant. Between days 18 and 21 all ovaries examined showed at least one large follicle. These findings suggest that in most of the cases follicular dynamics occurs in two wave-like patterns in the Egyptian buffalo cows.