Ultrasonographic Determination of Follicular Dynamics, Ovulation Timing, and Endocrine Profiles in Baggara Cattle (Bos indicus) Following an Ovsynch Protocol

Background: Reproductive efficiency in cattle production systems is constrained by inefficient estrus detection, particularly in indigenous breeds with subtle behavioral signs (Mukasa-Mugerwa, 1989). Fixed-time artificial insemination (FTAI) protocols like Ovsynch offer a solution but require breed-specific validation (Baruselli et al., 2017).

Objective: This study characterized ovarian follicular dynamics, ovulation timing, and associated endocrine profiles in Baggara cattle (Bos indicus) subjected to the Ovsynch protocol.

Methods: Twelve mature, non-lactating, non-pregnant Baggara cows (3-6 years, 350-420 kg) received the Ovsynch protocol: 1000 µg GnRH (Day 0), 500 µg PGF2α (Day 7), and 1000 µg GnRH (Day 9) (Pursley et al., 1995). Transrectal ultrasonography was performed every 4 hours after the second GnRH injection until ovulation. Blood samples were collected concurrently for ELISA analysis of follicle-stimulating hormone (FSH), luteinizing hormone (LH), estradiol-17β (E2), and progesterone (P4).

Results: The dominant follicle diameter increased progressively from 0.75±0.09 cm at 4 hours to 1.5±0.05 cm at 32 hours post-second GnRH. Ovulation occurred in 50% of cows between 32-36 hours and in 100% between 36-40 hours. Estradiol peaked at 24 hours (6.71±0.91 ng/mL), FSH at 32 hours (18.29±0.41 miu/mL), and LH at 28 hours (36.82±2.72 miu/mL). Progesterone showed a steady rise, reaching maximum concentration at 40 hours (2.72±0.23 pg/mL).

Conclusion: The Ovsynch protocol effectively synchronizes a predictable follicular wave in Baggara cattle, with ovulation occurring 36-40 hours after the second GnRH injection. These findings establish that fixedtime AI at approximately 20 hours post-second GnRH is optimally timed for this breed, providing a scientific basis for reproductive management improvement.

Keywords: Baggara Cattle, Ovsynch, Follicular Dynamics, Ovulation Synchronization, Fixed-Time AI, Reproductive Hormones.