Ovarian follicular dynamics monitored by real-time ultrasonography during oestrous cycle in buffalo (Bubalus bubalis)

Application of transrectal ultrasonography to buffaloes (n=6) to follow the growth of large antral follicles individually, on each day of one interovulatory interval revealed that follicular turnover during oestrous cycle occured in waves. There was a predominance of a two-wave pattern (516 animals) compared to that of a three-wave pattern (1/6 animals). For two-wave pattern, the first wave emerged at Day 0.20 +/- 0.19 (Day 0 = day of ovulation) and was marked by development of a dominant anovulatory follicle which grew in size from 5.40 +/- 0.24 mm at the day of detection to a maximum diameter of 12.40 +/- 0.81 mm on Day 5.60 +/- 1.57, with a growth rate of 0.88 +/- 0.17 mm/day and then regressed, with a mean persistence of 19.40 +/- 1.54 days. The second wave emerged at Day 9.20 +/- 1.06 and was marked by development of a dominant ovulatory follicle which grew in size from 4.20 +/- 0.37 mm at the day of detection to a maximum diameter of 13.80 +/- 0.37 mm on Day 21.00 +/- 1.38, with a growth rate of 0.66 +/- 0.12 mm/day and then ovulated on Day 21.60 +/- 1.25, with a mean persistence of 11.80 +/- 1.39 days. The maximum diameters attained and the growth rates of dominant anovulatory and dominant ovulatory follicles, and the mean number of follicles greater than or equal to 3 mm diameter detected at the time of emergence of first and second waves (11.80 +/- 1.74 and 9.00 +/- 2.81, respectively) were not significantly different. In the animal which showed a three-wave pattern, the first, second and third waves emerged on Days 1, 10 and 19, respectively. All animals, except one had at least one subordinate follicle In the first or second or both waves. The subordinate follicles increased in diameter over a few days and then regressed. The results indicate that in buffaloes, the follicular turnover during oestrous cycle occurs predominantly in a two-wave pattern.