Follicular Dynamics Following Estrus Synchronization in Swamp Buffalo Cows (Bubalus bubalis)

The objective of this study was to elucidate ovarian follicular dynamics in swamp buffalo cows (Bubalus bulalis) following a protocol for estrus synchronization during hot as low breeding season (March to June) and cool as high breeding season (November to February). Nine pluriparous buffalo cows received a progesterone ear implant for 10 days together with the administration of a luteolytic dose of PGF2 alpha at the time of implant removal to start the estrus cycle. Human Chorionic Gonadotrophin was administered whenever ovulation did not occur within the first five days following implant removal. Daily ultrasound monitoring and blood collection for progesterone values were performed starting one day following implant removal. The progesterone monitoring was used to confirm ovulation and to determine luteal function after ovulation. Data analysis was carried out at least for two consecutive cycles in each cycling buffalo in 22 estrus cycles. It was found that 5/22 (22.7%) were characterized by one wave and 17/22 (77.3%) by two waves of follicle development. Within cycles characterized by one wave of follicle development, emergence was recorded on day 2.3 +/- 0.5 and 1.8 +/- 0.4 during the low and high breeding season, respectively (p>0.05). Day of estrous cycle when the dominant follicle attained the largest size during the low and high breeding season was 13.5 +/- 1.2 and 12.6 +/- 1.5, respectively (p>0.05). Largest size (mm) of the dominant follicle during the low breeding and high season was 14.5 +/- 2.1 and 16.4 +/- 2.7, respectively (p>0.05). Within cycles with two follicular waves during the low breeding season, first and second wave emerged on day 1.2 +/- 0.3 and on day 11.4 +/- 0.8, respectively, and largest diameter of second wave dominant follicle (10.3 +/- 1.2 mm) was recorded on day 19.7 +/- 1.1. During the high breeding season, first and second wave emerged on day 0.9 +/- 0.4 and on day 10.7 +/- 0.9, respectively and largest diameter of second wave dominant follicle (12.8 +/- 1.2 mm) was recorded on day 18.9 +/- 1.7. Pooling data for both 1- and 2-wave cycles and seasons, mean progesterone value at estrus and ovulation was 0.07 +/- 0.03 ng/ml, but after ovulation mean progesterone increased to 2.37 +/- 0.5 ng/ml at the mid luteal phase and later, decreased at the late luteal phase which was 0.98 +/- 0.2 ng/ml. In conclusion, results from this study showed the first time of the typical pattern of follicle wave development in swamp buffalo.