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Equine veterinary journal2021; 54(2); 306-311; doi: 10.1111/evj.13455

hCG is more effective than the GnRH agonist buserelin for inducing the first ovulation of the breeding season in mares.

Abstract: Human Chorionic Gonadotropin (hCG) and Gonadotropin Releasing Hormone agonists (GnRHa) are routinely used to induce ovulation in mares. However, GnRHa efficacy in transitional mares has been suggested to be low. Objective: The aims of this study were as follows: (a) to compare the efficacy of hCG and GnRHa in inducing the first ovulation of the breeding season and (b) to evaluate the correlation between ovulatory response, uterine oedema and teasing score at the time of treatment during the early or late transitional phase. Methods: Randomised controlled superiority trial. Methods: Mares in winter anoestrus were treated with sulpiride when at least two follicles reached a diameter of 25 mm. The day after the follicle reached 35 mm in diameter, mares in oestrus were treated with GnRHa buserelin (N = 29) or hCG (N = 33) and checked daily for ovulation. Results: More mares (30/33, 90.1%) ovulated when the first ovulation after winter anoestrus was induced with hCG, than with GnRHa, (11/29, 38.0%) (P = .0001). Ovulation rate was lower in mares that did not show uterine oedema and full acceptance of the teaser stallion for at least three days before the treatment (32/41, 78% vs 9/21, 42.9%) P = .01. Conclusions: Plasma LH and oestrogen concentrations were not performed. Conclusions: These results demonstrate that hCG was more effective than GnRHa for inducing ovulation in the first cycle after winter anoestrus. Uterine oedema and behavioural signs of oestrus, for at least three days before the treatment, were predictors for a positive response to ovulation induction.
© 2021 The Authors. Equine Veterinary Journal published by John Wiley & Sons Ltd on behalf of EVJ Ltd.
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Publication Date: 2021-05-09 PubMed ID: 33884659PubMed Central: PMC9291952DOI: 10.1111/evj.13455Google Scholar: Lookup
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  • Journal Article
  • Randomized Controlled Trial
  • Veterinary

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 research investigates the effectiveness of two hormonal treatments, hCG and GnRHa, in inducing the first ovulation of the breeding season in mares, with hCG being found more effective.

Overview of the Study:

  • The research aimed to compare the efficiency of Human Chorionic Gonadotropin (hCG) and Gonadotropin Releasing Hormone agonists (GnRHa) in inducing the first ovulation of the breeding season in mares. It also aimed to understand the correlation between ovulatory response, uterine oedema (swelling), and teasing scores (often used to identify the onset of heat).
  • Both hCG and GnRHa are hormonal treatments commonly used to induce ovulation in mares. Recent studies suggested that the efficiency of GnRHa could be low on transitional mares – the mares transitioning from a non-breeding (anestrous) to a breeding (estrous) state.

Methodology:

  • The study structured itself as a randomized controlled superiority trial.
  • Mares in winter anoestrus (non-breeding period) were given sulpiride treatment when at least two of their follicles reached a diameter of 25mm.
  • When the follicle dimension reached 35mm, mares were treated with either GnRHa buserelin (29 mares) or hCG (33 mares).
  • The mares were then monitored daily for signs of ovulation.

Results:

  • The results demonstrated a notably higher ovulation rate in mares (90.1%) treated with hCG compared to GnRHa (38.0%).
  • Ovulation rates were lower in mares that did not exhibit uterine oedema and were less receptive to a teaser stallion, at least three days before treatment.

Implications and Conclusion:

  • The study concludes that hCG is more effective than GnRHa for inducing the first ovulation in mares after winter anoestrus.
  • The presence of uterine oedema and behavioural signs of estrus three days before treatment indicates a positive ovulation induction response.

Cite This Article

APA
Fanelli D, Tesi M, Rota A, Beltramo M, Conte G, Giorgi M, Barsotti G, Camillo F, Panzani D. (2021). hCG is more effective than the GnRH agonist buserelin for inducing the first ovulation of the breeding season in mares. Equine Vet J, 54(2), 306-311. https://doi.org/10.1111/evj.13455

Publication

Equine veterinary journal
ISSN: 2042-3306
NlmUniqueID: 0173320
Country: United States
Language: English
Volume: 54
Issue: 2
Pages: 306-311

Researcher Affiliations

Fanelli, Diana
  • Dipartimento di Scienze Veterinarie, Università di Pisa, Pisa, Italy.
Tesi, Matteo
  • Dipartimento di Scienze Veterinarie, Università di Pisa, Pisa, Italy.
Rota, Alessandra
  • Dipartimento di Scienze Veterinarie, Università di Pisa, Pisa, Italy.
Beltramo, Massimiliano
  • UMR Physiologie de la Reproduction et des Comportements (INRA, UMR85, CNRS, UMR7247, Université de Tours, IFCE), Nouzilly, France.
Conte, Giuseppe
  • Department of Agriculture, Food and Environment, University of Pisa, Pisa, Italy.
Giorgi, Mario
  • Dipartimento di Scienze Veterinarie, Università di Pisa, Pisa, Italy.
Barsotti, Giovanni
  • Dipartimento di Scienze Veterinarie, Università di Pisa, Pisa, Italy.
Camillo, Francesco
  • Dipartimento di Scienze Veterinarie, Università di Pisa, Pisa, Italy.
Panzani, Duccio
  • Dipartimento di Scienze Veterinarie, Università di Pisa, Pisa, Italy.

MeSH Terms

  • Animals
  • Breeding
  • Buserelin / pharmacology
  • Chorionic Gonadotropin / pharmacology
  • Female
  • Gonadotropin-Releasing Hormone / agonists
  • Horses
  • Male
  • Ovulation
  • Ovulation Induction / veterinary
  • Seasons

Grant Funding

  • PRA_2018_7 / University of Pisa

Conflict of Interest Statement

No competing interests have been declared.

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Citations

This article has been cited 2 times.
  1. Khan IU, Khairullah AR, Khan AY, Rehman AU, Mustofa I. Strategic approaches to improve equine breeding and stud farm outcomes. Vet World 2025 Feb;18(2):311-328.
    doi: 10.14202/vetworld.2025.311-328pubmed: 40182817google scholar: lookup
  2. Aboelmaaty AM, Elgharieb AEA, El-Debaky HA, Alkhadrawy JMH, Abou-Ahmed MM, Ghallab AM. Fluctuations of antimüllerian hormone, ovarian follicular reserve, and antioxidant status throughout the estrous cycle in aged mares. Open Vet J 2024 Nov;14(11):3132-3143.
    doi: 10.5455/OVJ.2024.v14.i11.44pubmed: 39737015google scholar: lookup
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