Comparison of fertility parameters in Romanov sheep synchronized with progesterone-based protocol plus PMSG or GnRH

Objective: The aim of this study was to compare the fertility parameters in response to pregnant mare serum gonadotropin (conventional treatment) or gonadotrophin-releasing hormone (alternative treatment) in Romanov sheep subjected to a 7-d short-term protocol out of breeding season. Materials and Methods: Sheep (n=57) received an intravaginal sponge impregnated with 20 mg fluorogestone acetate for 7 days and 125 µg cloprostenol at sponge removal. Sheep were randomly assigned to receive no treatment (CON, n=16), 240 IU pregnant mare serum gonadotropin (PMSG, n=24) at sponge removal or 10 µg busereline acetate (GnRH, n=17) at 30 h after sponge removal. Results: Estrous response and pregnancy rate were 86% and 75.4% in all sheep, respectively. Estrous response was numerically higher about 7% (p>0.05) in treatment groups (PMSG, 87.5%; GnRH, 88.2%) than CON (81.2%). However, pregnancy rate was numerically higher in PMSG (83.3%) than GnRH (70.6%) and CON (68.7%). As in pregnancy rate, lambing rate was approximately 15% numerically greater (p>0.05) in the PMSG (79.1%) than in GnRH (64.7%) and CON (62.5%) groups. Similarly, litter size numerically higher (p>0.05) in PMSG (2.1) than GnRH (1.9) and CON (1.9) groups. Conclusion: The use of GnRH offered similar estrous response compared to PMSG in Romanov sheep synchronized with short-term protocol. However, PMSG had numerically higher pregnancy rate, lambing rate, and litter size than GnRH. Considering the serious ethical concerns and animal welfare for the production of PMSG, it is necessary to use alternatively gonadotropins. Comprehensive studies are needed to compare the fertility parameters between PMSG and GnRH in Romanov sheep.