Comparison of the effect of Gonadotropin-Releasing Hormone and Human Chorionic Gonadotropin on Reproductive Performance of Romanov Ewes During the Natural Breeding Season

Document Type : Original Articles


1 Sarayan Faculty of Agriculture, University of Birjand, Birjand, Iran

2 Department of Agriculture, Payame Noor University, POX19395-3697, Tehran, Iran


Low pregnancy rate is an important issue in small ruminants. Superovulation protocols would serve as the possible techniques to increase the pregnancy rate in small ruminants due to the use of synthetic hormones. The present study aimed to assess the effect of gonadotropin-releasing hormone (GnRH) and Human chorionic gonadotropin (hCG) after artificial insemination (AI) on the pregnancy rate of Romanov ewes breed. To this end, estrus was synchronized in 140 ewes using a controlled internal drug-releasing (CIDR) device. Following CIDR removal, all ewes received 400 IU Pregnant Mare's Serum Gonadotropin (PMSG). The ewes were assigned to three groups (control, n=20; experimental groups, each of them was divided into three subgroups, n=20). The first group in each experiment was assumed as control. The second and third groups received three levels of GnRH, (400, 500, and 600 µg, n=20) and hCG (200, 300, and 400 IU) administered by the intramuscular (IM) route. As soon as the signs of estrus were observed, the ewes were isolated from the others and artificially inseminated with fresh sperm using the transcervical method. The results indicated that there were no significant differences between experimental groups in ovulation and pregnancy rates on days 33 and 90 post-AI (P>0.05). The highest twin birth rate (20%) was recorded in the hCG group (300 IU), as compared to GnRH and control groups (P<0.05). The effect of GnRH and hCG on the plasma concentration of progesterone was significant (P<0.01). The groups significantly differed in fecundity rate (Single birth, twin birth, and triple birth) (P<0.05), all of these parameters were significantly higher in the hCG 300 IU group. It can be concluded that the injection of 300 IU of hCG hormone after insemination improves pregnancy rate in ewes.


Main Subjects

  1. Dadashpour Davachi N, Zare Shahneh A, Kohram H, Zhandi M, Dashti S, Shamsi H, et al. In vitro ovine embryo production: the study of seasonal and oocyte recovery method effects. Iran Red Crescent Med J. 2014;16(9):e20749.
  2. Rekik M, Lassoued N, Yacoubi C. Reproductive performances in ewe lambs of the Queue Fine de l’Ouest breed and their D’Man crosses following synchronisation. Small Rumin Res. 2002;45(1):75-8.
  3. Fonseca J, Maffili V, Rodrigues M, Santos A, Rovay H, Neto AP, et al. Effects of hCG on progesterone concentrations and fertility in cyclic, lactating Alpine goats. Anim Reprod. 2018;3(4):410-4.
  4. Fukui Y, Itagaki R, Ishida N, Okada M. Effect of Different hCG Treatments on Fertility of Estrus-Induced and Artificially Inseminated Ewes During the Non-Breeding Season. J Reprod Dev. 2001;47(4):189-95.
  5. Dirandeh E, Masoumi R, Didarkhah M, Samadian F, Davachi ND, Colazo M. Effect of presynchronization prior to Ovsynch on ovulatory response to first GnRH, ovulatory follicle diameter and pregnancy per AI in multiparous Holstein cows during summer in Iran. Ann Anim Sci. 2018;18(3):713.
  6. Fonseca JF, Torres CA. Administration of hCG 5 days after breeding and reproductive performance in nulliparous dairy goats. Reprod Domest Anim. 2005;40(6):495-9.
  7. Lucy MC, Stevenson JS. Gonadotropin-releasing hormone at estrus: luteinizing hormone, estradiol, and progesterone during the periestrual and postinsemination periods in dairy cattle. Biol Reprod. 1986;35(2):300-11.
  8. Rostami B, Hajizadeh R, Shahir MH, Aliyari D. The effect of post-mating hCG or progesterone administration on reproductive performance of Afshari x Booroola-Merino crossbred ewes. Trop Anim Health Prod. 2017;49(2):245-50.
  9. Schmitt EJ, Diaz T, Barros CM, de la Sota RL, Drost M, Fredriksson EW, et al. Differential response of the luteal phase and fertility in cattle following ovulation of the first-wave follicle with human chorionic gonadotropin or an agonist of gonadotropin-releasing hormone. J Anim Sci. 1996;74(5):1074-83.
  10. Moeini M, Alipour F, Moghadam A. The effect of human chorionic gonadotropin on the reproduction performance in Lory sheep synchronized with different doses of pregnant mare serum gonadotrophin outside the breeding season. Asian J Anim Vet Adv. 2009;4(1):9-15.
  11. Thatcher WW, Moreira F, Santos JEP, Mattos RC, Lopes FL, Pancarci SM, et al. Effects of hormonal treatments on reproductive performance and embryo production. Theriogenology. 2001;55(1):75-89.
  12. Donovan A, Hanrahan JP, Kummen E, Duffy P, Boland MP. Fertility in the ewe following cervical insemination with fresh or frozen-thawed semen at a natural or synchronised oestrus. Anim Reprod Sci. 2004;84(3-4):359-68.
  13. García-Pintos C, Menchaca A. Pregnancy establishment and maintenance after the administration of equine chorionic gonadotropin (eCG) associated or not with gonadotropin-releasing hormone (GnRH) after insemination in sheep. Anim Prod Sci. 2018;58(10):1802-6.
  14. Ishida N, Okada M, Sebata K, Minato M, Fukui Y. Effects of GnRH and hCG Treatments for Enhancing Corpus Luteum Function to Increase Lambing Rate of Ewes Artificially Inseminated During the Non-Breeding Season. J Reprod Dev. 1999;45(1):73-9.
  15. Khan TH, Beck NF, Khalid M. The effects of GnRH analogue (buserelin) or hCG (Chorulon) on Day 12 of pregnancy on ovarian function, plasma hormone concentrations, conceptus growth and placentation in ewes and ewe lambs. Anim Reprod Sci. 2007;102(3-4):247-57.
  16. Kittok RJ, Stellflug JN, Lowry SR. Enhanced progesterone and pregnancy rate after gonadotropin administration in lactating ewes. J Anim Sci. 1983;56(3):652-5.
  17. Ahmadi E, Mirzaei A. High twin lambing rate of synchronized ewes using progestagen combined with the gonadotropins injection in breeding season. Rev Med Vet. 2016;167(1/2):28-32.
  18. Farin CE, Moeller CL, Mayan H, Gamboni F, Sawyer HR, Niswender GD. Effect of luteinizing hormone and human chorionic gonadotropin on cell populations in the ovine corpus luteum. Biol Reprod. 1988;38(2):413-21.
  19. Cam MA, Kuran M, Yildiz S, Selcuk E. Fetal growth and reproductive performance in ewes administered GnRH agonist on day 12 post-mating. Anim Reprod Sci. 2002;72(1):73-82.
  20. Bazer FW, Ott TL, Spencer TE. Maternal recognition of pregnancy: Comparative aspects: A review. Placenta. 1998;19:375-86.
  21. Mee MO, Stevenson JS, Alexander BM, Sasser RG. Administration of GnRH at estrus influences pregnancy rates, serum concentrations of LH, FSH, estradiol-17 beta, pregnancy-specific protein B, and progesterone, proportion of luteal cell types, and in vitro production of progesterone in dairy cows. J Animal Sci. 1993;71(1):185-98.
  22. Husein MQ, Ababneh MM. A new strategy for superior reproductive performance of ewes bred out-of-season utilizing progestagen supplement prior to withdrawal of intravaginal pessaries. Theriogenology. 2008;69(3):376-83.
  23. Quintero-Elisea JA, Macias-Cruz U, Alvarez-Valenzuela FD, Correa-Calderon A, Gonzalez-Reyna A, Lucero-Magana FA, et al. The effects of time and dose of pregnant mare serum gonadotropin (PMSG) on reproductive efficiency in hair sheep ewes. Trop Anim Health Prod. 2011;43(8):1567-73.
  1. Dadashpour Davachi N, Kohram H, Zeinoaldini S. Effect of the presence of corpus luteum on the ovary and the new oocyte recovery method on the oocyte recovery rate and meiotic competence of ovine oocytes. Afr J Biotechnol. 2011;10(47):9706-9.
  2. Diskin MG, Morris DG. Embryonic and early foetal losses in cattle and other ruminants. Reprod Domest Anim. 2008;43(2):260-7.
  3. Rhind SM, Chesworth JM, Robinson JJ. A seasonal difference in ovine peripheral plasma prolactin and progesterone concentrations in early pregnancy and in the relationship between the two hormones. J Reprod Infertil. 1978;52(1):79-81.