Acta Vet. Brno 2025, 94: 289-296
Evaluating the effect of GnRH on reproductive performance in nulliparous Assaf ewes
, Duygu Baki Acar2
1Çukurova University, Faculty of Ceyhan Veterinary Medicine, Department of Obstetrics and Gynecology, Adana, Türkiye
2Afyon Kocatepe University, Faculty of Veterinary Medicine, Department of Obstetrics and Gynecology, Afyonkarahisar, Türkiye
Received November 14, 2024
Accepted October 5, 2025
This study aimed to evaluate the effect of short-term progesterone-based oestrus synchronization protocol with or without gonadotropin-releasing hormone (GnRH) administration in nulliparous Assaf ewes at the end of the breeding season. Nulliparous ewes (n = 117) were randomly divided into three groups. Ewes in Group 1 received an intravaginal sponge and were injected with GnRH at the time of sponge insertion. On the day of sponge removal, all ewes received d-cloprostenol and 500 IU equine chorionic gonadotropin (eCG). In Group 2, the same treatment was received except for GnRH injection. Group 3 was designed as a control group, and no hormonal treatments were administered. The rams were joined into the herd for one ram for four ewes on day 8. The oestrus rates were similar in synchronization groups, 93.8% in Group 1 and 95.5% in Group 2, but higher than the control group (56.5%; P < 0.05). The pregnancy rates on day 25 were higher in the synchronization groups than in the control group (P < 0.001). The fertility rate was significantly higher in the synchronization groups than in the control group (P < 0.05). The fecundity and prolificacy rates tended to be higher in Group 2. These results suggest that nulliparous Assaf ewes can be synchronized successfully at the end of the season with short-term progesterone-based protocol. However, exogenous GnRH administration at the beginning of the protocol does not tend to improve fertility rates.
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Funding
The authors wish to thank Hatice Hızlı for the critical reading of statistical analyses of this paper. This manuscript was presented as an oral presentation at the joint Turkish and Italian International Animal Reproduction Congress (TIAR-2024) and the abstract was published in a Frontiers special issue.
