Effect of double GnRH injections on reproductive parameters in Awassi ewes receiving long-term progesterone

Changes on corpus luteum structure and progesterone synthesis pathway after hCG or GnRH treatment during the early luteal phase in sheep

This study investigated the effect of hCG or GnRH on structural changes of the corpora lutea (CL) and the regulation of the expression of steroidogenic enzymes involved in P4 secretion in post-ovulatory (po-CL) and accessory CL (acc-CL). Sixty-four ewes were assigned to three groups receiving: 300 IU of hCG (hCG) or 4 µg Buserelin (GnRH) or 1 mL of saline solution (Control) on Day (d) 4 post artificial insemination (FTAI). Laparoscopic ovarian were performed on d 4, 14 and, 21 post-FTAI to determine the numbers of CL. Blood samples were collected for serum LH and P4 analysis. On d 14 post-FTAI, both CL were removed from the ovary to determine large luteal cell (LLC) number and to evaluate the expression of steroidogenic enzymes (HSD3B1, STAR, CYP11A1). Only hCG and GnRH treated ewes generated acc-CL. The LLC in both po- and acc-CL were significantly greater in the hCG group compared to GnRH and Control groups (P<0.05). Overall, hCG group showed the greatest immunodetection of HSD3B1and STAR in both po- and acc-CL (P<0.05). rnRNA expression of HSD3B1, STAR and CYP11A1 in the acc-CL tended to be greater in hCG group than in GnRH group (P<0.1). The LH concentration was increased in GnRH group (P<0.05) and P4 concentration was greater in hCG group compared to the other groups (P<0.05). In conclusion, administration of hCG has a notably impact on acc-CL development and the expression of steroidogenic enzymes compared to GnRH treatment in ewes. This leads to elevated P4 concentration and improved luteal function.

Effect of PGF2α and GnRH administration on reproductive performance in Ghezel ewes

The main aim of the current study was to evaluate the effect of GnRH administration on day five after mating as well as PGF2α injection at the time of CIDR removal on the reproductive performance of Ghezel ewes. Estrus synchronization was performed using an intravaginal application of CIDR for 14 days and injection of 500 IU of PMSG at the time of CIDR removal. A total of 114 healthy fat-tailed ewes were randomly allotted into three groups as follow: control group (n = 35), did not receive any additional treatment; PG group (n = 44), each ewe received a dose of PGF2α at the time of CIDR removal; and PG+GnRH group (n = 35), the ewes received a dose of PGF2α at the time of CIDR removal and a single dose of GnRH, five days post-mating (post-conceptional day (PCD)- 5). Body condition score (BCS) of total ewes was determined at the time of CIDR insert. Blood samples were collected on PCD-19 for determining the serum progesterone levels. All the ewes were examined by transrectal ultrasonography 30-35 days after mating for pregnancy diagnosis. The serum values for P4 concentration were in control, PG and PG+GnRH groups 6.34 ± 1.17, 9.19 ± 2.55 and 10.57 ± 2.0 ng/mL respectively. The PG+GnRH treatment significantly increased the litter size compared to the control group (P = 0.04), but there were no significant differences in another reproductive indices between experimental groups. The multiple birth, twin, fecundity rates and litter size (P = 0.05, p = 0.03 and p = 0.003 respectively) were significantly higher in ewes with BCS > 2 compared to ewes with BCS ≤ 2. It is concluded that GnRH on PCD-5 treatment in addition to PGF2α injection at the time of CIDR removal could improve reproductive performance of Qezel ewes during non-breeding season.

The effect of double-dose GnRH injections on reproductive performance parameters following short-term progestagen administration in lactated Awassi ewes during the non-breeding season

The present study was aimed to investigate the effects of double-dose gonadotropin-releasing hormone (GnRH) injection on the induction of oestrus and some reproductive performance parameters in Awassi ewes during the non-breeding season. In the study, 100 ewes were treated with a vaginal sponge containing 60 mg medroxyprogesterone acetate for 7 days in the anoestrus (day 0). PMSG 500 IU and 250 μg cloprostenol sodium were injected on the day of removal of the sponge (day 7). Ewes in Group 1 (n = 31) were not subjected to any hormonal treatment. Ewes in Group 2 (n = 31) were given 50 μg GnRH 48th hour after removal of the sponge. Ewes in Group 3 (n = 33) were given 50 μg GnRH 48th hour after the removal of the sponge and 50 μg GnRH 12th day after post-mating. The results obtained in the study showed that there were no statistical differences between the Groups 1, 2 and 3 in terms of oestrus rates (82.8%, 68.9%, 72.7%), conception rates (66.7%, 55.0%, 54.2%), multiple pregnancy rates (28.5%, 50.0%, 30.7%) and litter sizes (1.28, 1.50, 1.31). No significant increases in P4 concentration were observed in Group 3 treated with GnRH at the 12th day after post-mating; however, a numerically lower (p > 0.05) late embryonic-early fetal mortality rate was observed in Group 3 (0%), when compared with the values obtained in Group 1 (12.5%) and Group 2 (9.1%). In conclusion, after short-term progestagen administration during the non-breeding season, double-dose GnRH injections did not increase P4 concentration and had no significant differences on reproductive performance parameters among groups.

The effect of prostaglandin and gonadotrophins (GnRH and hCG) injection combined with the ram effect on progesterone concentrations and reproductive performance of Karakul ewes during the non-breeding season

The effect of prostaglandin and gonadotrophins (GnRH and hCG) combined with the ram effect on the progesterone (P4) concentrations and reproductive performance of Karakul ewes was investigated during non‐breeding season. Ewes (n = 93) received a male effect and were divided into two treatment groups including GnRH ‐ hCG (hCG, n = 32), GnRH ‐ GnRH (GnRH, n = 30) and a control (n = 31) group. This study was carried out from April (hormonal injection) to October (lambing). The first doses of GnRH (4.2 μg, Buserelin) were injected at the beginning of the study in treatment groups. These ewes were treated with hCG (250 IU) or the second GnRH dose five days later. All animals received two injections (ten days apart) of 150 μg PGF2α five days after the hCG or the second GnRH injection. Mating was initiated two days after the second prostaglandin injection and lasted for 34 days. Blood samples were collected by jugular venipuncture on days −10, −5, 0 (first PGF2α injection), 17 and 30 during the study. Pregnancy diagnosis was performed through transabdominal ultrasonography on day 40 after the removing of ram. Conception rate was 93.8, 90 and 87.1% in the hCG, GnRH and control groups, respectively. Lambing rate tended to increase in the hCG group compared with the control group (87.1 versus 58.1%; p < .1). There was no significant difference in P4 concentrations among studied groups in identical sampling times (p > .05). In conclusion, the administration of prostaglandin and hCG in combination with the ram effect tended to decrease lambing period. In other words this protocol tended to increase lambing rate at the first cycle. Treatment with hCG or GnRH did not increase serum P4 concentrations of treated Karakul ewes during the non‐breeding season.