Effects of a GnRH antagonist on antral follicular development and ovarian hemodynamics in cycling ewes

Sixteen multiparous Santa Inês ewes underwent transrectal ovarian ultrasonography from days 6 to 17 (D6-17; D0 = ovulation). On D6, ewes received a single subcutaneous injection of Firmagon® at a low dose (LD; n = 5; 215 µg/kg body weight b.w.) or a high dose (HD; n = 6; 235 µg/kg b.w.); controls (C; n = 5) received saline. Ovulations were detected in 100% of controls, but only in 20% of LD and 17% of HD animals. Mean daily numbers of large antral follicles (> 4.49 mm) decreased (P ® treatment was associated with a reduced number of large antral follicles and alterations in ovarian blood perfusion.