Follicular dynamics and colour Doppler vascularity evaluations of follicles and corpus luteum in relation to plasma progesterone during the oestrous cycle of Surti buffaloes.

With an objective to evaluate the follicular dynamics and vascularity changes in follicles and corpus luteum, the ovaries of cyclic Surti buffaloes (n = 9) were examined daily sequentially by transrectal B-mode and colour flow mode (CFM) ultrasonography starting from the day of oestrus till the onset of next oestrus. Higher proportion of buffaloes evidenced one-wave cycle (66.66%) compared to two-wave cycle (33.34%) with none showing a three-wave cycle. The dominant follicle of the first follicular wave was the ovulatory follicle and persisted for 19.70 ± 0.50 days compared to its persistence for 16.5 ± 1.45 days in a two-wave cycle. The maximum diameter of the ovulatory follicle in a one-wave and two-wave cycle did not differ yet their linear growth rates were significantly lower (p < 0.01) in a one-wave cycle. Colour flow mode examination of follicles revealed that the percentage of follicles with detectable blood flow in the subsequently determined largest follicle (dominant follicle) was not different from that in the second largest follicle before follicle deviation. The blood flow in the dominant follicle increased significantly on the day of oestrus. The mean diameter and blood flow to the corpus luteum (CL) increased linearly and significantly from Day 5 of oestrus till Day 13 after which both parameters started declining. At or around Day 16, there was precipitous fall in the blood supply to the CL and CL diameter that continued declining thereafter to reach the lowest around Day 20 of the oestrous cycle. Rise in plasma progesterone concentrations was synchronous to CL diameter and vascularity and showed significant and positive correlations. It was concluded that Surti buffaloes evidence a preponderance of one-wave follicular growth pattern with a significant increase in the vascularity of ovulatory follicle on the day of oestrus and corpus luteum on Day 13 of the oestrous cycle.