Follicular waves during the oestrous cycle in Nili-Ravi buffaloes undergoing spontaneous and PGF2α-induced luteolysis

The objective of this study was to characterize the follicular waves and associated ovarian events during spontaneous and PGF2α-induced oestrous cycles in Nili-Ravi buffaloes. In Exp. 1, (n = 13 oestrous cycles) follicular and luteal development was monitored by ultrasonography and jugular blood samples were collected simultaneously on alternate days. Of 12 oestrous cycles, 9 (75%) had two waves of follicular activity and only 3 (25%) had three waves. The mean (±S.E.M.) length of the oestrous cycle was shorter (P < 0.05) in buffaloes with two waves than in those with three waves (21.2 ± 0.1 days versus 22.8 ± 0.1 days). In Exp. 2, follicular dynamics were compared in buffaloes undergoing spontaneous (n = 12 oestrous cycles) and PGF2α-induced (n = 9) regression of the corpus luteum (CL). The dynamics of ovulatory follicular growth during the 3 days before oestrus were similar (P > 0.05) in buffaloes undergoing spontaneous and PGF2α-induced luteolysis. These results show that (1) the majority of buffaloes had a two wave pattern of follicular growth and emergence of a third wave was associated with a longer luteal phase, and (2) follicular dynamics during the 3 days before oestrus were similar in buffaloes undergoing spontaneous and PGF2α-induced luteolysis.