Follicular activity and hormonal secretory profile in vicuna ( Vicugna vicugna)

• Published in: Theriogenology 2004-02, Vol.61 (4), p.663-671
• Main Authors: Miragaya, M.H, Aba, M.A, Capdevielle, E.F, Ferrer, M.S, Chaves, M.G, Rutter, B, Agüero, A
• Format: Article
• Language: English
• Subjects: Animals; Camelids, New World - physiology; diameter; Estradiol - blood; Estradiol-17β; Female; Follicular activity; follicular development; Ovarian Follicle - physiology; ovarian follicles; Ovary - diagnostic imaging; Ovary - physiology; Progesterone; Progesterone - blood; Time Factors; Ultrasonography; Vicuna; vicunas
• ISSN: 0093-691X; 1879-3231
• DOI: 10.1016/S0093-691X(03)00238-3

The objective of the present study was to characterize ovarian activity in non-mated vicunas, relating ovarian structures (evaluated by transrectal ultrasonography, daily for 30 days) to changes in plasma concentrations of estradiol-17β and progesterone. Ovarian follicular activity occurred in waves, characterized by the follicle emergence, growth and regression. The mean duration of follicular waves was 7.2±0.5 days (mean±S.E.M.), with a range of 4–11 days. The follicular growth phase averaged 3.0±0.2 days, the static phase 1.4±0.1, the regression phase 2.9±0.3 days, and the inter-wave interval was 4.2±0.3 days. The mean growth rate during the growing phase was 1.8±0.1 mm/day, while the duration of the interval from 6 mm to maximum diameter was 1.4±0.1 days. The mean maximum diameter of the dominant follicle was 8.4±0.3 mm (range: 6.2–11.2) and mean diameter of the largest subordinate follicle was 5.4±0.1 mm. There was an inverse relationship between the size of the largest follicle and the total number of follicles ( r=−0.21, P=0.002). Follicle activity alternated between ovaries in 77% of the waves, with 40% of dominant follicles present in the left ovary and 60% in the right ovary. Plasma estradiol-17β concentrations also had a wave-like pattern, varying between 12.0 and 62.8 pmol/l. Plasma progesterone concentrations remained below 5.0 nmol/l and there was no ultrasonographic evidence of ovulation during the study.