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Veterinary medicine and science2025; 12(1); e70697; doi: 10.1002/vms3.70697

Progestagens Monitoring in 147 Mares in Order to Induce Foaling With Oxytocin.

Abstract: A total of 147 mares of different breeds (110 were sport or race horses, often very valuable) have been monitored over 5 years from 2012 to 2016. When at or near term, the mares were monitored in order to induce foaling, by checking the mammary development by palpation, analysing the colour and consistency of the precolostrum, estimating the calcium and antibodies concentrations in the precolostrum and by measuring the plasmatic progestagens concentration every day at 6 p.m. At the end of gestation, it has been observed that the progestagens rate levelled off (the top concentration varies from mare to mare: it can be as low as 35 ng/mL or up to 260 ng/mL) before falling sharply. Parturition was induced when the progestagens concentration fell of about 50% within 24 to 48 h. Induction was performed at 9 p.m. in 93 mares that followed the rule of the drop of progestagens (to respect the nycthemeral cycle) by a single IM oxytocin injection from 10 to 50 UI according to the weight of the mare (120 to 900 kg). Following the oxytocin injection, 90% (n = 84) of the foals were born within 20 to 50 min, 7.5% after 60 min (usually due to an excess of volume or dystocia), all alive and viable. Thirty to 60 min after birth, a manual delivery was performed for 71% (n = 66) of the mares. Among the 54 mares with spontaneous parturition (not induced because of insufficient proof of imminent birth), all foals were alive except for 2 twins that were found dead. A manual delivery was necessary for 17% (n = 9) of them. A 50% drop of the progestagens concentration is a good indication of the imminence of foaling: It is then safe to induce foaling, which usually results in a higher probability for a healthy foal and a reduced risk of genital lesions to the mare. Au cours de 5 saisons de monte entre 2012 et 2016, 147 juments de races différentes, dont 110 juments de selle, souvent de valeur, appartenant à différents propriétaires, ont été confiées pour surveillance du poulinage.A la date du terme ou à l'approche du terme, elles ont été suivies en se basant sur le développement de la mamelle(palpation), la couleur et la consistance du précolostrum(traite), complétés par une estimation quotidienne de la teneur en calcium et en anticorps du précolostrum et un dosage des progestagènes plasmatiques. Le taux de progestagènes évolue en plateau en fin de gestation mais, selon les juments, il est très variable, il peut osciller autour de 35 ng/mL ou beaucoup plus, le record a été de 260 ng/mL. Lorsqu'il chute d'environ 50% en 24 à 48 h, la parturition a, alors, été déclenchée chez 93 juments, par une injection de 10 à 50 UI d'ocytocine, en fonction de leur poids(120 à 900 kg) par la voie I.M., à 21 h pour respecter le rythme nycthéméral des poulinages.Tous les poulains sont nés vivants et viables:90% 20à 50 mn après l'injection,7.5% plus de 60mn plus tard (excès de volume ou dystocies).Trente à 60mn plus tard, 71% des juments sont délivrées manuellement. Chez les 54 témoins (qui ne répondaient pas à tous les critères retenus ou qui poulinaient entre 19 h, dosage des progestagènes, et 21 h, heure prévue pour l'injection d'ocytocine), tous les poulains sont vivants sauf 2 jumeaux retrouvés morts. La délivrance manuelle a été nécessaire chez 17% d'entre elles. Une chute de 50% du taux de progestagènes permet donc d'induire le poulinage sans risque de prématurité du poulain ce qui augmente les chances d'avoir un poulain vivant et une jument sans lésion génitale grave. SUMMARY: A 50% drop of the progestagens concentration within 24 to 48 h indicates imminent parturition Progestagens blood concentration, udder development, and precolostrum monitored together allows generally to determine the night of parturition A healthy foal is obtained if parturition is induced after the fall in blood progestagens associated with sufficient udder development and quality of colostrum.
© 2025 The Author(s). Veterinary Medicine and Science published by John Wiley & Sons Ltd.
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Publication Date: 2025-11-27 PubMed ID: 41306086PubMed Central: PMC12658334DOI: 10.1002/vms3.70697Google Scholar: Lookup
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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.

Overview

  • This study monitored 147 pregnant mares to identify precise physiological signs indicating imminent foaling and safely induce birth with oxytocin, aiming to improve foal survival and reduce health risks to mares.

Study Design and Population

  • Sample: 147 mares of various breeds, with 110 being sport or race horses, considered valuable.
  • Duration: Monitored over 5 breeding seasons from 2012 to 2016.
  • Owners: Mares belonged to multiple owners and were under veterinary surveillance near term.

Monitoring Parameters and Methods

  • Daily measurements done every day at 6 p.m., including:
    • Plasma progestagen concentration.
    • Mammary gland development assessed by palpation.
    • Analysis of precolostrum color and consistency.
    • Estimations of calcium and antibody concentrations in precolostrum.
  • Purpose: These parameters helped estimate the optimal timing for foaling induction.
  • Note: Progestagen levels varied widely among mares (from ~35 ng/mL up to 260 ng/mL) but plateaued near term before a sharp decline.

Key Finding: Progestagen Drop as Indicator for Imminent Foaling

  • A consistent fall of about 50% in plasma progestagen concentration within 24 to 48 hours signaled the approach of parturition.
  • This biomarker was used as a primary criterion to decide when to induce foaling safely.

Induction Protocol

  • Induction performed on 93 mares that exhibited the 50% progestagen drop, respecting the mare’s natural daily rhythm by administering oxytocin at 9 p.m.
  • Oxytocin dose varied between 10 to 50 International Units (IU), adjusted according to the mare’s weight (120 to 900 kg).
  • Injection method: Intramuscular (IM).

Outcomes of Induced Foaling

  • High success rate with 90% of foals born within 20 to 50 minutes post-oxytocin administration.
  • 7.5% of foals were born after more than 60 minutes, typically due to large foal volume or dystocia.
  • All foals from induced mares were alive and viable.
  • Manual placental delivery was performed in 71% of these mares, between 30 to 60 minutes after birth.

Outcomes of Spontaneous Foaling (Control Group)

  • 54 mares that did not meet all criteria for induction or foaled spontaneously were observed.
  • All foals were viable except for two dead twins.
  • Manual placental delivery was necessary for 17% of these mares.

Conclusions and Implications

  • A 50% decrease in progestagen concentration within 1-2 days before expected foaling is a reliable marker for imminent delivery.
  • Using this alongside assessments of udder development and precolostrum quality allows veterinarians to time induction accurately.
  • Inducing foaling after progestagen drop and confirming physical readiness results in a high probability of healthy foals and minimizes risks of premature birth.
  • Induced foaling also reduces potential for severe genital injuries in mares by better timing and facilitating parturition.

Additional Notes

  • The timing of oxytocin administration at 9 p.m. took into account the mare’s natural nycthemeral (daily) rhythm to enhance induction success.
  • The study combined hormonal, physical, and biochemical markers to create a comprehensive monitoring strategy for safer foaling management.
  • This approach is particularly valuable for valuable sport or racehorses where foal viability and mare health are critical.

Cite This Article

APA
Tainturier D, Tainturier B, Michaud S, Briand-Amirat L, Topie E, Moreno D. (2025). Progestagens Monitoring in 147 Mares in Order to Induce Foaling With Oxytocin. Vet Med Sci, 12(1), e70697. https://doi.org/10.1002/vms3.70697

Publication

Veterinary medicine and science
ISSN: 2053-1095
NlmUniqueID: 101678837
Country: England
Language: English
Volume: 12
Issue: 1
Pages: e70697
PII: e70697

Researcher Affiliations

Tainturier, Daniel
  • Biotechnology and Pathology of Reproduction, Nantes-Atlantic National College of Veterinary Medicine, Food Science and Engineering, Oniris, Nantes Cedex, France.
Tainturier, Benoit
  • French Military Service, 23ème Groupe Vétérinaire, Garde Républicaine, Paris Cedex, France.
Michaud, Sandrine
  • Biotechnology and Pathology of Reproduction, Nantes-Atlantic National College of Veterinary Medicine, Food Science and Engineering, Oniris, Nantes Cedex, France.
Briand-Amirat, Lamia
  • Biotechnology and Pathology of Reproduction, Nantes-Atlantic National College of Veterinary Medicine, Food Science and Engineering, Oniris, Nantes Cedex, France.
Topie, Emmanuel
  • Biotechnology and Pathology of Reproduction, Nantes-Atlantic National College of Veterinary Medicine, Food Science and Engineering, Oniris, Nantes Cedex, France.
Moreno, Diego
  • Biotechnology and Pathology of Reproduction, Nantes-Atlantic National College of Veterinary Medicine, Food Science and Engineering, Oniris, Nantes Cedex, France.

MeSH Terms

  • Animals
  • Horses / physiology
  • Horses / blood
  • Female
  • Oxytocin / administration & dosage
  • Oxytocin / pharmacology
  • Progestins / blood
  • Pregnancy
  • Parturition / drug effects
  • Oxytocics / administration & dosage
  • Oxytocics / pharmacology

Conflict of Interest Statement

None of the authors have any conflicts of interest to declare.

References

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