OVARIAN FOLLICULAR DYNAMICS DURING THE ESTROUS-CYCLE IN BUFFALO (BUBALUS-BUBALIS)

The growth, selection, regression and ovulation of ovarian follicles w as ultrasonically monitored in 30 Murrah buffalo throughout a spontane ous estrous cycle during the breeding season (autumn). Examinations re vealed that follicular growth during the estrous cycle occurs in waves ; the buffalo showed 1-wave (3.3%, n=1), 2-wave (63.3%, n=19) or 3-wav e (33.3%, n=10) follicular growth. The first wave began at 1.00, 1.16 +/- 0.50 and 1.10 +/- 0.32 d in buffalo with 1, 2 and 3 waves, respect ively (ovulation = Day 0). The second wave appeared at 10.83 +/- 1.09 and 9.30 +/- 1.25 d (P < 0.01) for the 2 and 3 wave cycle animals, res pectively. The third wave started at 16.80 +/- 1.22 d. Structural pers istence of the first dominant follicle was longer in the 2- than S-wav e cycles (20.67 +/- 1.18 vs 17.90 +/- 3.47 d; P < 0.05). The duration of the growth and static phases of the first dominant follicle differe d between the 2 and 3 wave cycles (P < 0.05), whereas there were no di fferences in linear growth rates (cm/d). Two and three wave cycles dif fered (P < 0.05) with respect to the maximum diameter of both the firs t dominant follicle (1.51 +/- 0.24 vs 1.33 +/- 0.18 cm) and the ovulat ory follicles (1.55 +/- 0.16 vs 1.34 +/- 0.13 on). No relationship was found between dominant follicle development and the presence of eithe r a CL or a previous dominant follicle in either ovary. Two and three wave cycles also differed with respect to the mean length of intervals between ovulation (22.27 +/- 0.89 vs 24.50 +/- 1.88 d; P < 0.01) and the mean length of luteal phases (10.40 +/- 2.11 vs 12.66 +/- 2.91 d; P < 0.05). These results demonstrate that buffalo have estrous cycles with ?, 2 or 3 follicular waves; that 2-wave cycles are the most commo n; and that the number of waves in a cycle is associated with the lute al phase and with estrous cycle length. (C) 1997 by Elsevier Science I nc.