Effect of Exogenous GnRH at the Time of Artificial Insemination on Reproductive Performance of Awassi Ewes Synchronized with Progestagen–PMSG–PGF_2α Combination

Abstract

This study was carried out to investigate the efficacy of PGF(2alpha) for oestrus synchronization (ES) in Awassi ewes to which were administered the progestagen-PMSG combination, and to evaluate the effect of the exogenous GnRH administration immediately after the artificial insemination (AI) on their pregnancy rate and lambing performance during the breeding season. The ewes (n = 33) were treated with an intravaginal sponge impregnated with 30 mg fluorogestane acetate for 12 days and were injected with 500 IU PMSG at the time of removal of the sponge. The ewes were then divided into three equal groups of 11 ewes each. One millilitre of physiological saline (0.9% NaCl; placebo) was administered to each ewe in Group 1 at the time of second AI. Approximately 4 microg GnRH (busereline) was injected to each ewe in Group 2 immediately after second AI. A total of 150 microg PGF(2alpha) (cloprostenole) was injected at the time of sponge removal on day 12 and 4 microg GnRH immediately after the second AI was also treated to each ewe in Group 3. Intracervical AI with diluted fresh semen was performed twice at 12 and 24 h following the onset of oestrus. The injection-oestrus onset and injection-oestrus-end interval in Group 3 was significantly (p < 0.001) shorter than both Groups 1 and 2. Although the pregnancy rates of Groups 2 and 3 (81.8%; 9/11) were numerically higher than of Group 1 (63.6%; 7/11), the difference among the groups was statistically insignificant. The multiple birth rate of Group 3 was found higher than Groups 1 and 2. However, the number of single lambs of Group 1 was also higher than Groups 2 and 3 (p < 0.05). Despite the litter sizes of Groups 2 (1.27; 14/11) and 3 (1.55; 17/11) being numerically higher than Group 1 (0.73; 8/11), the differences among all the groups were statistically insignificant. In conclusion, the administration of PGF(2alpha) at the time of removal of the sponge shortens the injection oestrus-onset and oestrus-end interval in Awassi ewes treated with progestagen-PMSG. Additionally, exogenous GnRH treatment immediately after the AI increases the multiple birth rate of Awassi ewes synchronized with progestagen-PMSG-PGF(2alpha) combination.

Effect of PMSG administration in combination with vaginal sponge on estrous occurrence and litter size of Javanese sheep

“…Group 1, treated with only MPA, has a similar result to those found in group 3. However, both results are higher than that reported by Turk et al (2008) using 30 mg progestagen-500 IU PMSG combination. The slight discrepancy between the results obtained in the current study and those previous findings may be due to differences in the breed of sheep used and environmental condition, such as season in which the study was conducted.…”

“…In principle, litter size can be increased by controlling follicle stimulating hormone (FSH) regulation in the bloodstream. Administration of pregnant mare serum gonadotropin (PMSG) can increase multiple birth rate in breeds characterised by low litter size (Boscos et al, 2002;Turk et al, 2008). The use of PMSG in combination with MAP was characterised by 114.6% of multiple births proportion (Koyuncu and Alticekic, 2010), and compact induction was found in the combination rather than in MAP alone (Dogan and Nur, 2006).…”

Effects of GnRH administration on ovulation and fertility in ewes subjected to estrous synchronization

“…Besides that, the findings agree with results of Ekiz et al (2009), who reported a longer estrous duration (34.80±2.15 hours) when estrous was synchronized with fluorgestone acetate intravaginal sponges left for 14 days, plus an injection of 600 IU PMSG at the time of sponge removal and ewes were exposed to ram twice a day than when remaining with the ram permanently (15.60±1.83 hours). Turk et al (2008) reported 29.9 h after progestagen, PMSG and prostaglandin treatment.…”

Awassi sheep reproduction and milk production: review

“…The duration of pregnancy was not affected by either the type of birth (146±6.0 to 153.6± 3.6 days for singles, 148.7±1.2 to 153.3±4.4 days for twins, and 144 to 146.5±0.5 days for triplet) or the sex (152.1± 1.4 days for males and 151.0±1.5 days for females). In addition, estrous synchronization programs during or outside the breeding season have no effect on the duration of pregnancy in Awassi ewes Turk et al 2008). …”