Ultrasonographic characterization of ovarian follicular development in the Indian blackbuck antelope (Antilope cervicapra)

Transrectal ultrasonography was used to monitor the ovarian follicular dynamics in the Indian blackbuck antelope (Antilope cervicapra). The blackbuck has a short oestrous cycle (mean length 15.3 ± 0.8 days) and exhibits two follicular waves, with a mean time of 14.3 ± 0.8 and 8.9 ± 0.6 days for the first and second waves, respectively. The mean diameter of the preovulatory follicles was 0.54 ± 0.04 cm, and only a single ovulatory follicle resulted from the second follicular wave in all the hinds. Follicular activity and preovulatory follicles appeared alternatively on the ovaries in successive cycles. The plasma estradiol-17 (E2) concentrations also exhibited a wave-like pattern, varying between 1.3 ± 0.01 pg ml−1 and 5.3 ± 1.9 pg ml−1. A positive relationship (r = 0.85) was recorded between the dominant follicle diameter and the plasma E2 concentrations during the oestrous cycle. Furthermore, this baseline ultrasound data, in particular the diameter of the preovulatory follicle, enabled the team to carry out fixed-time AI, leading to live offspring in this native threatened species. This study, for the first time, documents the use of transrectal ultrasonography to monitor ovarian follicular dynamics in the Indian blackbuck antelope. It was also successful in the application and the development of a protocol for fixed-time AI in the Indian blackbuck antelope