Effect of buserelin on follicular dynamics and hormonal secretory profile in vicuna (Vicugna vicugna)

AGÜERO, A.; ABA, M.A.; CAPDIEVELLE, E.F.; CHAVES, M.G.; RUTTER, B.; BIANCHI, C.P.; MIRAGAYA, M.H.

Journal of Camel Practice and Research

Camel Publishing Home

Lugar: India; Año: 2005 p. 149 - 153

0971-6777

The aim of the study was to evaluate the effect of an injection of the GnRH analogue buserelin in vicuñas with a dominant follicle. Follicular dynamics was monitored daily during 12 days by transrectal ultrasonography and blood samples were collected on each day in non-pregnat, non lactating vicunas. In treated animals, the day a dominant follicle was first detected, 8 micrograms of buserelin were injected intravenously. Mean follicle diameter the day of buserelin injection (day 0) was 7.97. Thereafter, mean follicle diameter decreased to 5.41 ± on day 1, 3.2 0.35 mm"on day 2, and varied between 3.5 and < until day 7 when the lowest mean follicle size (2.2 ± 0.21 mm">0.21 mm) was recorded. In control animals, after attainment of dominance (day 0) follicles remained growing until day 1 and thereafter started to regress. In addition, all control animals showed development of a new dominant follicle immediately after the regression of the initial one. Conversely, no dominant follicles were recorded in treated animals after ovulation. Mean progesterone concentrations remained low (around 1 nmol l) until day 4 after treatment, when they started to sharply increase. Peak concentrations (30.23 ± 9.57 nmol) were recorded on day 8 after buserelin injection and had decreased to 8.13 ± 2.54 nmol l. In control animals, progesterone concentrations remained close to 1 nmol l-1 throughout the study.  In treated animals, maximun estradiol-17beta plasma concentrations were recorded on day 0 (38.35 ± 4.26 pmol l-1). Thereafter, mean plasma concentrations steadily decreased until day 3 when its lowest concentrations were recorded (18.26 ± 1.78 pmol l-1). On day 4, mean concentrations started to increase until day 6 (28.01 ± 3.52 pmol l-1). In control animals, concentrations remained close to those recorded on day 0 until the end of the study. In conclusion, buserelin injection in the presence of a dominant follicle induces ovulation in vicunas. In addition, the presence of endogenous progesterone from an active corpus luteum was shown to have a negative effect on follicle dynamics. This action could be used in future to synchronize the emergence of a new follicular wave.