Effects of GnRH and hCG Treatments for Enhancing Corpus Luteum Function to Increase Lambing Rate of Ewes Artificially Inseminated During the Non-Breeding Season.

Abstract

Abstract.Two experiments were conducted to enhance the corpus luteum (CL) function for increasing lambing rate of ewes treated with GnRH or hCG after artificial insemination (AI) during the non-breeding season. Ewes (Experiment 1: n=102, Experiment 2: n=37) were pretreated with a controlled internal drug release dispenser (CIDR) for 12 days and 500 IU equine chorionic gonadotropin (eCG) 1 day before CIDR removal. In Experiment 1, the ewes were treated on Day 12 (Day 0=CIDR removal): 1) Group I; GnRH (100 µg), 2) Group II; hCG (500 IU), 3) Group III; 0.6% saline (2 ml) for control. Pregnancy and lambing rates and prolificacy were not significantly different among the groups. But, there was significant (P<0.01) difference in the lambing rate between parous (27%) and non-parous (72%) in Group I. On Day 17, plasma progesterone (P4) levels of Group I were significantly (P<0.01) lower than those of Group III, but on the contrary, the plasma P4 levels of Group II were significantly (P<0.01) higher than those of Group III. In Experiment 2, the ewes were treated: 1) Group I; hCG (500 IU) on Day 6, 2) Group II; hCG (500 IU) on Day 9, 3) Group III; no treatment for control. Pregnancy and lambing rates and prolificacy were not significantly different among the groups, but on Days 12 and 15, the plasma P4 levels of Groups I and II were significantly (P<0.01) higher than those of Group III. The present results indicate that a single hCG treatment on Days 6, 9 and 12 after CIDR removal stimulates CL and increased P4 concentration, but the increased P4 levels did not reflect on the fertility of treated ewes.

Human chorionic gonadotropin increases serum progesterone, number of corpora lutea and angiogenic factors in pregnant sheep

“…1A). Our results agree with other studies in sheep (Nephew et al 1994, Ishida et al 1999, Fukui et al 2001 and cattle (Santos et al 2001, Stevenson et al 2007) demonstrating hCG treatment results in greater serum P 4 concentrations. It has been postulated that the increased serum concentrations of P 4 may be due to increased accessory CL formation or increased number of luteal cells secreting P 4 (Fricke et al 1993, Schmitt et al 1996, Santos et al 2001, Effects of hCG during early pregnancy in sheep Stevenson et al 2007).…”

Comparison of Fertility of Estrous Synchronized Ewes with Four Different Intravaginal Devices during the Breeding Season.

“…On Farm B, on Day 21, all inseminated ewes were bled to measure the plasma progesterone (P 4 ) concentration for the determination of conception (more than 2.0 ng/ml) according to the result of Ishida et al [24]. The ewes on both Farms A and B were allowed to term to record the lambing rate (no.…”

Comparison of Hormonal Treatment Kisspeptin with GnRH and hCG on the some Reproductive Performance of Cyprus, Does during Non-Breeding Season

“…A strategy of reproductive performance included inducing estrus and ovulation (Cameron et al, 1988;Khan et al, 2003;González-Álvarez et al 2016).The hCG has an activity similar to luteinizing hormone (LH), while the GnRH acts on the pituitary gland, stimulates the release of LH and FSH and subsequently the secretion of steroid hormones from the gonads. These hormones when administrated in the luteal phase act indirectly or directly on the ovary generating the formation of an accessory corpus luteum and increasing the serum progesterone concentration (Ishida et al,1999;Lankford et al, 2010). Increased the progesterone concentration (Moeini et al, 2013) led to improve the embryo survival (Lashari and Tasawar, 2010) and accelerate embryonic development and improve pregnancy rates (Nephew et al, 1994).…”