Ovulation induction in ewes using GnRH in long and short-term synchronization protocols

ABSTRACT

This study was done to evaluate the efficiency of GnRH along with long-term and short-term synchronization protocols on ovulation induction and corpus luteum development. Ewes underwent four protocols Long+GnRH (n = 11) with vaginal sponge (60 mg MAP) for 12 days along with 300 IU of eCG on day 12 and 0.025 mg of GnRH 27 h after sponge removal; Long (n = 10) with vaginal sponge for 12 days along with 300 IU of eCG on day 12; Short GnRH (n = 10) with vaginal sponge for 7 days along with 37.5 μg of D-cloprostenol on day 5 and 300 IU of eCG on day 7, plus 0.025 mg of GnRH used 27 h after sponge removal; and Short (n = 10) with vaginal sponge for 7 days. D-cloprostenol (37.5 μg) was administered on day 5 and eCG (300 IU) was administered on day 7.Ovulation was evaluated 52, 56, 60, 66, 72, 76 h after sponge removal. Blood was collected twelve days after sponge removal to measure progesterone concentration. On this same day, the corpus luteum was measure and counted. When GnRH was used, all ewes ovulated, while 70 and 80% of ewes ovulated in protocols that had not received GnRH (Long and Short, respectively). The GnRH accelerated ovulation (P< 0.05) in relation to sponge removal in both protocols and induced ovulation in approximately 28 h. The GnRH Was effective in inducing ovulation without decreasing the corpus luteum volume and progesterone concentration.