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

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 during non-breeding season. All sheep (n:57) were subjected to short-term synchronization protocol. Intravaginal sponge impregnated with 20 mg fluorogestone acetate was inserted for 7 days and all sheep received 125 µg cloprostenol at sponge removal. Sheep were randomly assigned to receive no additional treatment (CON, n:16), 240 IU pregnant mare serum gonadotropin (PMSG, n:24) at sponge removal or 10 µg buserelin acetate (GnRH, n:17) at 30 h after sponge removal. Natural mating was performed following detection of estrous with fertile eight Romanov rams. Estrous response, pregnancy rate, lambing rate, and litter size were compared among groups. 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 (p>0.05) in PMSG (83.3%) than GnRH (70.6%) and CON (68.7%). Similarly, lambing rate in the PMSG (79.1%) was approximately 15% numerically greater (p>0.05) than in GnRH (64.7%) and CON (62.5%). In addition, litter size in PMSG (2.1) was also numerically higher (p>0.05) than GnRH (1.9) and CON (1.9).The use of GnRH provided similar estrous response compared to use of PMSG in Romanov sheep synchronized with short-term protocol. However, use of PMSG provided numerically higher pregnancy rate, lambing rate, and litter size than use of GnRH. Considering the serious ethical concerns and animal welfare for the production of PMSG, it is necessary to use alternative gonadotropins. Comprehensive studies are needed to compare the fertility parameters between application of PMSG and GnRH in Romanov sheep.