Document Type : Research Paper
Authors
1 Department of Animal Science, Faculty of Agriculture, Lorestan University, Khorramabad, Iran.
2 2- Animal production sector, Agricultural Organization, Khoramabad
Abstract
Reduced progesterone (P4) concentrations following mating have been associated with the development of smaller, underdeveloped embryos, leading to increased rates of embryonic mortality. The primary objective of this study was to elucidate the effects of administration of Pregnant Mare Serum Gonadotropin (PMSG) or Gonadotropin-Releasing Hormone (GnRH) post-insemination on the reproductive performance of Lori ewes during the anestrus season. 75 Lori ewes were randomly assigned to three treatment groups in a completely randomized design (CRD) experiment. Initially, all ewes were subjected to estrous synchronization using intravaginal sponges. The ewes were randomly allocated to one of three treatment groups post-insemination on the fourth day. The first group received an intramuscular injection of 5 mL of GnRH, the second group was administered 300 IU of PMSG, and the control group received 1 mL of saline solution. Progesterone levels were measured on the 14th day post-insemination, and pregnancy status was confirmed by ultrasonography on the 40th day. Finally, reproductive parameters were recorded and data analysis was performed using SAS software. The results indicated that GnRH-treated ewes exhibited significantly higher lambing rates (68.00%) and fecundity rates (0.76%) in comparison to their PMSG-treated counterparts (36.00% and 0.48%, respectively) and the control group (32.00% and 0.32%, respectively). Furthermore, both GnRH and PMSG treatments resulted in significantly higher P4 levels on the 14th day post-insemination compared to the control group. These findings suggest that administering GnRH on the fourth day post-insemination can substantially enhance lambing and fecundity rates in Lori ewes during the non-breeding season.
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