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Home / Equine Research Bank / Acta Vet Scand / A preliminary study on the induction of dioestrous ovulation...
Acta veterinaria Scandinavica2006; 48(1); 12; doi: 10.1186/1751-0147-48-12

A preliminary study on the induction of dioestrous ovulation in the mare–a possible method for inducing prolonged luteal phase.

Abstract: Strong oestrous symptoms in the mare can cause problems with racing, training and handling. Since long-acting progesterone treatment is not permitted in mares at competition (e.g. according to FEI rules), there is a need for methods to suppress unwanted cyclicity. Spontaneous dioestrous ovulations in the late luteal phase may cause a prolongation of the luteal phase in mares. Methods: In this preliminary study, in an attempt to induce ovulation during the luteal phase, human chorionic gonadotropin (hCG) (3000 IU) was injected intramuscularly in four mares (experimental group) in the luteal phase when a dioestrous follicle > or = 30 mm was detected. A fifth mare included in this group was not treated due to no detectable dioestrous follicles > or = 30 mm. Four control mares were similarly injected with saline. The mares were followed with ultrasound for 72 hours post injection or until ovulation. Blood samples for progesterone analysis were obtained twice weekly for one month and thereafter once weekly for another two to four months. Results: Three of the hCG-treated mares ovulated within 72 hours after treatment and developed prolonged luteal phases of 58, 68 and 82 days respectively. One treated mare never ovulated after the hCG injection and progesterone levels fell below 3 nmol/l nine days post treatment. Progesterone levels in the control mares were below 3 nmol/l within nine days after saline injection, except for one mare, which developed a spontaneously prolonged luteal phase of 72 days. Conclusions: HCG treatment may be a method to induce prolonged luteal phases in the mare provided there is a dioestrous follicle > or = 30 mm that ovulates post-treatment. However, the method needs to be tested on a larger number of mares to be able to draw conclusions regarding its effectiveness.
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Publication Date: 2006-07-26 PubMed ID: 16987391PubMed Central: PMC1557516DOI: 10.1186/1751-0147-48-12Google Scholar: Lookup
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  • Comparative Study
  • Journal Article

Summary

This research summary has been generated with artificial intelligence and may contain errors and omissions. Refer to the original study to confirm details provided. Submit correction.

The study explores the use of human chorionic gonadotropin (hCG) to induce prolonged luteal phases in mares, as a method to suppress reproductive cycles that can disrupt horse training and competition.

Research Context

The study is rooted in the issues that arise from strong oestrous symptoms in mares. These symptoms can interfere with the horse’s performance during races, training, or generally affect their behaviour. Prescriptive treatments like long-acting progesterone are not allowed in competition mares. Consequently, there is a necessity for alternative ways to suppress these disruptive cycles. One such approach investigated was the induction of dioestrous ovulations in the late luteal phase, which usually results in prolonged luteal phases for mares.

Methodology

  • The study experimented with human chorionic gonadotropin (hCG) to induce ovulation during the luteal phase.
  • An initial sample of four mares was selected and each received an intramuscular injection of 3000 IU hCG when a dioestrous follicle of equal to or more than 30 mm was identified.
  • A fifth mare in the study didn’t receive the treatment due to the absence of a large enough dioestrous follicle.
  • Four control mares were injected with saline in identical conditions.
  • Post-injection, the mares were monitored using ultrasound for 72 hours or until ovulation occurred.
  • Blood samples were taken twice weekly for a month, followed by once weekly for the next two to four months for progesterone analysis.

Results

  • Three of the four hCG-treated mares ovulated within 72 hours of treatment, resulting in prolonged luteal phases of 58, 68, and 82 days respectively.
  • One treated mare didn’t ovulate after the hCG injection and displayed progesterone levels below 3 nmol/l nine days post-treatment.
  • Among the control mares, progesterone levels fell below 3 nmol/l within nine days after saline injection, except for one mare that spontaneously developed a prolonged luteal phase of 72 days.

Conclusions and Recommendations

The study concluded that hCG treatment could be a viable method to induce prolonged luteal phases in mares when a dioestrous follicle of 30 mm or larger is present and ovulates post-treatment. However, the authors caution that more extensive experimentation with a larger sample size is needed to definitively establish the effectiveness of the method.

Cite This Article

APA
Hedberg Y, Dalin AM, Santesson M, Kindahl H. (2006). A preliminary study on the induction of dioestrous ovulation in the mare–a possible method for inducing prolonged luteal phase. Acta Vet Scand, 48(1), 12. https://doi.org/10.1186/1751-0147-48-12

Publication

Acta veterinaria Scandinavica
ISSN: 1751-0147
NlmUniqueID: 0370400
Country: England
Language: English
Volume: 48
Issue: 1
Pages: 12

Researcher Affiliations

Hedberg, Ylva
  • Division of Comparative Reproduction, Obstetrics and Udder Health, Department of Clinical Sciences, P,O, Box 7054, Swedish University of Agricultural Sciences, SE-750 07 Uppsala, Sweden. ylva.hedberg@kv.slu.se
Dalin, Anne-Marie
    Santesson, Malin
      Kindahl, Hans

        MeSH Terms

        • Animals
        • Chorionic Gonadotropin / administration & dosage
        • Chorionic Gonadotropin / pharmacology
        • Diestrus / drug effects
        • Diestrus / physiology
        • Female
        • Horses / physiology
        • Injections, Intramuscular / veterinary
        • Luteal Phase / drug effects
        • Ovulation / drug effects
        • Ovulation Induction / veterinary
        • Progesterone / blood
        • Random Allocation
        • Sodium Chloride / pharmacology

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        Citations

        This article has been cited 1 times.
        1. Aurich C, Kaps M. Suppression of reproductive behaviour and gonadal function in female horses-An update.. Reprod Domest Anim 2022 Sep;57 Suppl 4(Suppl 4):4-12.
          doi: 10.1111/rda.14129pubmed: 35467049google scholar: lookup
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