Ultrasound of follicular development and ovulation in induced estrus in Sahelian goats

Abstract

Follicular development and ovulation occurrence have been studied in induced estrus in Sahelian goats. Fifteen females of average ages and weights of 37.25 ± 1.5 months and 32.5 ± 7.3 kg, respectively, with parity between 1 and 3, were treated with intravaginal sponges (fluorogestone acetate, 20 mg/sponge) for 11 days. This treatment was combined with intramuscular administration per animal of 400 IU of equine chorionic gonadotropin (eCG) and 2 ml of cloprostenol on day nine. Estrus detection was performed by visual observation after the introduction of two fertile male goats in the herd. Follicular development was monitored by ultrasound at 12-hour intervals using a 5-MHz linear probe. Mean time to estrus onset was 15.4 ± 2.9 hours. Estrus was characterized by vulval discharge and mounting attempts between congeners. Its average duration was 32.3 ± 3.8 hours. At the end of treatment, 13 follicles were observed on the right ovary and 13 on the left one with mean diameters of 5.26 ± 1.25 mm and 4.73 ± 1.45 mm, respectively. The mean diameter of preovulatory follicles was 7.6 ± 2.1 mm. This diameter varied according to the ovary. Seventeen ovulations were recorded, and eight occurred 45‒50 hours after the end of treatment. These results are valuable benchmarks for the application of reproductive biotechnology to this breed.