The effect of double-dose GnRH injections on reproductive performance parameters following short-term progestagen administration in lactated Awassi ewes during the non-breeding season

The present study was aimed to investigate the effects of double-dose gonadotropin-releasing hormone (GnRH) injection on the induction of oestrus and some reproductive performance parameters in Awassi ewes during the non-breeding season. In the study, 100 ewes were treated with a vaginal sponge containing 60 mg medroxyprogesterone acetate for 7 days in the anoestrus (day 0). PMSG 500 IU and 250 μg cloprostenol sodium were injected on the day of removal of the sponge (day 7). Ewes in Group 1 (n = 31) were not subjected to any hormonal treatment. Ewes in Group 2 (n = 31) were given 50 μg GnRH 48th hour after removal of the sponge. Ewes in Group 3 (n = 33) were given 50 μg GnRH 48th hour after the removal of the sponge and 50 μg GnRH 12th day after post-mating. The results obtained in the study showed that there were no statistical differences between the Groups 1, 2 and 3 in terms of oestrus rates (82.8%, 68.9%, 72.7%), conception rates (66.7%, 55.0%, 54.2%), multiple pregnancy rates (28.5%, 50.0%, 30.7%) and litter sizes (1.28, 1.50, 1.31). No significant increases in P4 concentration were observed in Group 3 treated with GnRH at the 12th day after post-mating; however, a numerically lower (p > 0.05) late embryonic-early fetal mortality rate was observed in Group 3 (0%), when compared with the values obtained in Group 1 (12.5%) and Group 2 (9.1%). In conclusion, after short-term progestagen administration during the non-breeding season, double-dose GnRH injections did not increase P4 concentration and had no significant differences on reproductive performance parameters among groups