Is one-wave follicular growth during the estrous cycle a usual phenomenon in water buffaloes ( Bubalus bubalis)?

Abstract

The pattern of growth and regression of ovarian follicles was monitored once daily for one complete estrous cycle in eight individual water buffaloes by ultrasonographic scanning of the ovaries for an entire interovulatory interval of normal cycle length. One-wave follicular growth was observed in five animals and two-wave follicular growth in three buffaloes during the estrous cycle. The first follicular wave of a two-wave cycle emerged significantly earlier ( P < 0.05) than the emergence of the solitary wave of a one-wave cycle. One- and two-wave cycles differed significantly ( P < 0.05) with respect to the mean interovulatory interval (21.0 ± 0.54 days versus 22.7 ± 0.33 days) and the mean interestrus interval (20.8 ± 0.58 days versus 22.3 ± 0.66 days). The overall linear growth rate of the ovulatory follicle was significantly greater ( P < 0.01) in a two-wave cycle compared to that of a one-wave cycle (1.17 ± 0.33 mm/day versus 0.32 ± 0.01 mm/day). In a one-wave pattern, the growth profile of the solitary dominant follicle was atypical, showing three distinct phases, i.e. growth phase, regression phase and regrowth phase culminating in ovulation. The level of plasma progesterone steadily increased from day 0 of estrous cycle, attained peak level on day 14 and declined thereafter. A slower growth rate of the dominant follicle was observed in the presence of higher plasma progesterone concentration. The present study shows that one-wave follicular growth is a normal phenomenon in suckled water buffaloes.