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Home / Equine Research Bank / Can Vet J / Deslorelin and naltrexone stimulate follicular development i...
The Canadian veterinary journal = La revue veterinaire canadienne2019; 60(8); 855-858;

Deslorelin and naltrexone stimulate follicular development in mares during autumn transition and early anestrus.

Abstract: Horses are long-day breeders and commence ovarian follicular activity during the spring. Evidence suggests that there is an endogenous circannual rhythm in mares, and it is uncertain whether hormonal manipulation during or immediately following the fall transition induces follicular development. The current study was designed to test the hypothesis that both deslorelin and naltrexone induce follicular development in late fall transitioning or anestrous mares. Five of six mares treated with deslorelin, and 4 of 6 mares treated with naltrexone, developed a pre-ovulatory-sized follicle and were inseminated. Zero of three deslorelin-control mares and 1 of 3 naltrexone-control mares were inseminated. The number of mares bred in the deslorelin treatment group was significantly higher than in the corresponding control group ( < 0.05). Six of nine mares inseminated were pregnant 14 days after insemination. In conclusion, we were able to induce follicular development resulting in fertile ovulations during and shortly after the fall transition. . Les chevaux sont des reproducteurs saisonniers influencés par la lumière du jour et l’activité folliculaire ovarienne débute au printemps. Les évidences suggèrent que chez les juments il y a un rythme circannuel endogène, et il est incertain si une manipulation hormonale durant ou immédiatement après la transition automnale induit le développement folliculaire. La présente étude a été conçue afin de vérifier l’hypothèse que le deslorelin et le naltrexone induisent le développement folliculaire tard à l’automne lors de la période de transition ou chez des juments en anoestrus. Cinq des six juments traitées avec du deslorin et quatre des six juments traitées avec du naltrexone ont développé un follicule de taille pré-ovulatoire et ont été inséminées. Aucune des trois juments témoins pour le deslorin et une des trois juments témoins pour le naltrexone furent inséminées. Le nombre de juments saillies dans le groupe de traitement deslorin était significativement supérieur à celui du groupe témoin correspondant (P < 0,05). Six des neuf juments inséminées étaient gestantes 14 jours après l’insémination. En conclusion, nous avons été en mesure d’induire le développement folliculaire résultant en des ovulations fertiles durant et tôt après la transition automnale.(Traduit par D Serge Messier).
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Publication Date: 2019-08-09 PubMed ID: 31391602PubMed Central: PMC6625173
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  • Journal Article

Summary

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The research article suggests that hormonal treatments with deslorelin and naltrexone can effectively stimulate ovarian follicular development in mares during late fall, leading to successful inseminations.

Objective of the Study

The objective of this study was to evaluate the effects of hormonal treatments – specifically with deslorelin and naltrexone – on ovarian follicular development in mares during late fall transition and early anestrus stages. The hypothesis was that these treatments would induce development in mares, thereby leading to successful inseminations.

Methods and Treatment Groups

  • The study involved several groups of mares which were treated with either deslorelin or naltrexone.
  • Controls for both treatments were also maintained.
  • The treatments were administered during late fall transition and early anestrus stages.
  • The test subjects were monitored for appearance of pre-ovulatory-sized follicles, which was followed by insemination.

Findings of the Study

The study found that the treatments had a significant impact on follicular development in mares:

  • Five out of six mares treated with deslorelin developed a pre-ovulatory-sized follicle and were inseminated.
  • Four out of six mares in the naltrexone group showed similar results.
  • None of the deslorelin-control mares and only one of the naltrexone-control mares developed a pre-ovulatory-sized follicle and were inseminated.
  • The number of mares bred in the deslorelin treatment group was significantly higher than in the corresponding control group.

Conclusion of the Study

The hormonal treatments – deslorelin and naltrexone – were found to effectively induce follicular development in mares during the fall transition and early anestrus stages. Not only did this result in successful inseminations, but it also led to pregnancies, as 6 out of the 9 inseminated mares were found to be pregnant 14 days after insemination. These findings suggest that it could be possible to manipulate the breeding season of mares through the use of these hormonal treatments.

Cite This Article

APA
Kwong GPS, Klein C. (2019). Deslorelin and naltrexone stimulate follicular development in mares during autumn transition and early anestrus. Can Vet J, 60(8), 855-858.

Publication

The Canadian veterinary journal = La revue veterinaire canadienne
ISSN: 0008-5286
NlmUniqueID: 0004653
Country: Canada
Language: English
Volume: 60
Issue: 8
Pages: 855-858

Researcher Affiliations

Kwong, Grace P S
  • Faculty of Veterinary Medicine, University of Calgary, 3280 Hospital Drive NW, Calgary, Alberta T2N 4Z6.
Klein, Claudia
  • Faculty of Veterinary Medicine, University of Calgary, 3280 Hospital Drive NW, Calgary, Alberta T2N 4Z6.

MeSH Terms

  • Anestrus
  • Animals
  • Female
  • Horses
  • Naltrexone
  • Ovulation
  • Pregnancy
  • Triptorelin Pamoate / analogs & derivatives

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Citations

This article has been cited 1 times.
  1. Bukhari SSUH, Urooj S. Retinol and cholecalciferol affect buserelin-induced estrous in anestrous mares. Trop Anim Health Prod 2025 Mar 17;57(3):124.
    doi: 10.1007/s11250-025-04369-9pubmed: 40095200google scholar: lookup
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