Superovulation in mares: Limitations and perspectives

Alvarenga, Marco Antônio; Carmo, M. T.; Landim-Alvarenga, Fernanda da Cruz

doi:10.21836/pem20080118

Cited by 18 publications

(15 citation statements)

References 9 publications

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“…MOET has tremendous potential for the horse industry, since mares are mono-ovulatory animals and usually require two or three natural cycles in order to establish a pregnancy (Ball 2000). Moreover, MOET applications in mares are hampered by their low sensibility to hormones used to increase follicular growth and multiple ovulations in other species (Alvarenga et al 2008).…”

Section: Introductionmentioning

confidence: 99%

Induction of multiple ovulations in mares using low doses of GnRH agonist Deslorelin Acetate at 48 hours after luteolysis

Azevedo¹,

Souza²,

Ferreira-Silva³

et al. 2015

PHK

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Summary: This study was aimed to test low doses of a GnRH agonist, deslorelin acetate (DA), for induction of multiple ovulations in mares and to determine its impact upon their reproductive efficiency. Seven mares aging from 8 -20 years were used in three consecutive reproductive cycles. Mares were initially monitored by ultrasound irrespectively of cycle stage, inseminated and submitted to embryo collection (EC) (T1). Immediately after, mares received 7.5 mg dinoprost tromothamine (DT) and were monitored by ultrasound twice a day until larger follicle reached 23 -25 mm and the second >18 mm (T2). At this time point, mares received 100 µg DA and ovulation was induced with 1000 µg DA and 1000 IU hCG when largest follicle reached 33 -35 mm in diameter, followed by EC. Mares were further allocated to T3 when received 7.5 mg DT after EC on T2 and 100 µg DA 48 h later. DA treatment was performed until dominant follicle reached 34 ±1 mm or 6 days of application. All EC were performed 8 days after ovulation. Mares with multiple ovulations in T1, T2 and T3 were 14.28 % (1/7), 100.00 % (7/7) and 0.00 % (0/7), respectively, and averaged 0.43 ± 0.53 in T1, 0.86 ± 0.38 in T2 and 0.00 in T3 embryos per donor, respectively. Embryo recovery rate was 43.00 % in T1, 85.71 % in T2 and 0.00 % T3. In conclusion, use of DA in mares with follicles larger than 25mm enhanced dominant and co-dominant follicle growth, that ultimately increased the incidence of multiple ovulations and embryo recovery rate.

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Section: Introductionmentioning

confidence: 99%

Induction of multiple ovulations in mares using low doses of GnRH agonist Deslorelin Acetate at 48 hours after luteolysis

Azevedo¹,

Souza²,

Ferreira-Silva³

et al. 2015

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“…The GnRH is a natural ovulation-inducing factor, although it has a short half-life [34]. The synthetic analogs of GnRH such as Buserelin [6,17], Deslorelin [1,3,4], and Histrelin [26,30,39], have greater potency and longer half-life confers greater structural and metabolic stability than its natural form [24]. Collectively, all these compounds have been considered as capable of inducing ovulation in mares.…”

Section: Introductionmentioning

confidence: 99%

Induction of Ovulation in Mangalarga Marchador Mares by hCG or GnRH

Ferreira-Silva¹,

Nascimento²,

Moura³

et al. 2018

Acta Scientiae. Vet.

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Background: Induction of ovulation is a key procedure for horse assisted reproduction technologies, such as for artificial insemination (AI) and embryo transfer. The application of hCG remains as the primary ovulation-inducing agent for horse assisted reproduction, but alternatives are in demand to avoid its adverse effects, such as loss of ovulation-inducing efficiency over multiple applications by hCC-antibody production. Despite reports on alternative ovulation-inducing agents, pair-wise comparisons of such agents under similar conditions have been limited. Under such scenario, the work was aimed to determine the efficiency of both hCG and Buserelin at inducing ovulation in Mangalarga Marchador mares raised in the Northeast of Brazil under an AI program.Materials, Methods & Results: Mares were initially selected based on their reproductive performance, the absence of clinical-reproductive alterations and adequate body condition score. Mares in diestrus were randomly distributed in three experimental conditions, received 5 mg of Dinoprost and were monitored daily for estrus detection. After estrus detection, ovaries were monitored by ultrasonography, in 12-h intervals, until the follicle reached 35 mm. At this time-point, ovulation was induced with 0.042 mg of Buserelin endovenously, with 3,000 IU hCG by an intramuscular shot, and control mares received 2 mL of saline solution, also by an intramuscular shot. Both hCG and Buserelin displayed similar efficiencies (P > 0.05) for induction of ovulation and that both agents were effective (P < 0.05) for such purpose, since greater percentages (P < 0.05) of induction on mares treated from those of the control. Moreover, the total number of ovulations in mares treated at the end of the experiment was not different (P > 0.05) from those found in the Control. All ovulations occurred within a 72-h period after treatment. It can be observed that in mares treated with hCG or Buserelin, ovulations occurred both in more mares (P < 0.05) and at earlier time-points than mares from the control. It is also possible to note that pregnancy was not different (P > 0.05) between hCG and Buserelin groups, and that pregnancy of mares treated with ovulation-inducing factors was similar to the control.Discussion: The majority of ovulations in mares occurred within initial 48-h after treatment for both hCG and GnRH, suggesting a similar potential for horse assisted reproduction. Both hCG and Buserelin are two commonly used agents for induction of ovulation in mares. As described here, the majority of ovulations occurred within initial 48-h after treatment, a fact which can be attributed to hCG and GnRH activity, since it can happen in intervals from 36 to 48-h after treatment. Pregnancy rates did not differ among groups. These results are under the working hypothesis that hCG and Buserelin would display similar efficiencies on pregnancy rates. Despite the understanding of hCG activity on induction of ovulation due to its high specificity toward LH receptors and results from a direct effect on diminishing estradiol concentration, increasing LH, and further inducing ovulation within 48-h after treatment. In contrast, Buserelin has a similar functional property but acts upon LH synthesis and its release. In conclusion, ovulation in mares can be induced with both hCG and Buserelin, and both ovulation-inducing agents do not affect pregnancy rates.Keywords: gonadotropin, releasing factor, ovary, follicle, corpus luteum.

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“…However, the number of embryos recovered for each ovulation in mares induced to multiple ovulations has still been low and close Use of Equine Pituitary Extract (EPE) in low doses to induce double ovulation in mares to that one presented by mares with natural ovulation, around 0.5 embryos. Several products have been employed in order to increase follicles number for mares ovulation as Porcine Follicle Stimulating Hormone (p-FSH) (Cullingford et al, 2010), Equine Chorionic Gonadotrofin (ECG) and Gonadotropin Releasing Hormone (GnRH) (Farquhar et al, 2000), Equine Pituitary Extract (EPE) (Alvarenga et al, 2001(Alvarenga et al, , 2008, purified Extract of Equine Follicle Stimulating Hormone (e-FSH), (Köllmann et al, 2008) and more recently, Deslorelin Acetate (Azevedo et al, 2015). Due to the fact that results have widely varied, research is directed to protocols using EPE and FSH, re-FSH and re-LH combination and Deslorelin Acetate (Bertozzo et al, 2012).…”

Section: Introductionmentioning

confidence: 99%