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Equine veterinary journal2025; doi: 10.1111/evj.70083

Cortisol and heart rate response of mares during the in-hand breeding procedure with and without restraint.

Abstract: In-hand breeding involving restraint methods is likely the most common practice in the horse breeding industry worldwide. However, welfare issues that arise from such management have not been investigated in detail. Objective: (1) To investigate whether the mares show increased stress responses during in-hand breeding using (a) a lip twitch and (b) hobbles. (2) To evaluate if the use of restraint methods influences the mare's expression of oestrous behaviour. Methods: Intra-individual cross-over design. Methods: Six Franches-Montagnes stallions and 10 warmblood mares were used in these experiments. Each mare underwent standardised teasing and breeding sessions with and without one of the two restraint methods (morning and afternoon) on the day before ovulation. Salivary cortisol concentrations, continuous heart rate (HR) and heart rate variability (HRV) before, during and after the teasing and breeding sessions were measured as objective stress indicators. An ethogram was established to evaluate the behaviour during breeding. Results: Using the lip twitch increased cortisol concentrations (with twitch from 0.77 ± 0.07 to 1.20 ± 0.07 ng/mL vs. without twitch from 0.73 ± 0.07 ng/mL to 0.99 ± 0.07 ng/mL; p = 0.04), and the hobbles could not be applied to 2 out of the 10 mares in our study, as they did not tolerate this restraint method. Conclusions: The sample contained a small number of mares. Conclusions: Using a lip twitch in mares during in-hand breeding is accompanied by a slight degree of stress, while hobbles are tolerated very well or not at all by the mares.
© 2025 The Author(s). Equine Veterinary Journal published by John Wiley & Sons Ltd on behalf of EVJ Ltd.
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Publication Date: 2025-09-02 PubMed ID: 40891633DOI: 10.1111/evj.70083Google Scholar: Lookup
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  • 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.

Overview

  • This study examined how two different restraint methods, a lip twitch and hobbles, affect stress levels and behavior in mares during in-hand breeding procedures.
  • It aimed to determine whether these restraint techniques cause stress and influence mares’ oestrous behaviors using physiological and behavioral measures.

Background and Purpose

  • In-hand breeding, where mares are physically restrained, is a common practice in horse breeding worldwide.
  • Despite its widespread use, how restraint affects the welfare, particularly stress levels, of mares has not been thoroughly studied.
  • The study focused on two main objectives:
    • To assess if using a lip twitch or hobbles during breeding induces increased stress responses in mares.
    • To evaluate whether these restraint methods alter how mares express behaviors associated with oestrus (the period of sexual receptivity).

Methods

  • The study utilized an intra-individual cross-over design, meaning each mare experienced both restrained and non-restrained breeding sessions to allow direct comparison within individuals.
  • Subjects:
    • Six Franches-Montagnes stallions and ten warmblood mares were involved.
    • Trials were conducted on the day before ovulation, a critical time for observing oestrous behavior and breeding responses.
  • Procedure:
    • Mares underwent standardized teasing (to stimulate oestrous behavior) and breeding sessions either with restraint (lip twitch or hobbles) or without restraint.
    • Two sessions were conducted on the same day: one in the morning and one in the afternoon.
  • Stress and behavior evaluation:
    • Salivary cortisol concentrations were measured as a biochemical marker of stress.
    • Heart rate (HR) and heart rate variability (HRV) were continuously monitored to assess physiological stress responses.
    • An ethogram (a catalog of specific behaviors) was used to quantify oestrous behavior during breeding.

Results

  • Use of the lip twitch restraint:
    • Significantly increased salivary cortisol levels from a baseline of approximately 0.77 ng/mL to 1.20 ng/mL, signaling increased physiological stress.
    • Without the twitch, cortisol also rose but to a lesser extent (from about 0.73 to 0.99 ng/mL).
    • The increase with lip twitch was statistically significant (p = 0.04), indicating a measurable effect on stress.
  • Use of hobbles:
    • Hobbles were either well tolerated or not tolerated at all by different mares—2 out of 10 mares refused to accept this form of restraint.
    • The study did not report a significant cortisol increase due to hobbles for the mares that tolerated it.
  • Effects on oestrous behavior:
    • The abstract does not detail specific findings related to behavior changes induced by restraints, suggesting either minimal effect or that the primary focus was on physiological stress markers.
  • Limitations:
    • The sample size was relatively small, especially considering only 10 mares were tested.
    • This limits broad generalizability but provides preliminary insight into restraint impacts on stress.

Conclusions

  • Applying a lip twitch to mares during in-hand breeding produces a measurable, though slight, increase in stress as indicated by cortisol increase.
  • Hobbles present a dichotomous response: mares either tolerate them very well or refuse them completely, indicating individual variation in acceptability.
  • These findings highlight welfare considerations in horse breeding management—lip twitches may raise stress levels modestly, and hobbles might cause behavioral issues in some mares.
  • The study emphasizes the need for careful choice and potentially individualized restraint methods to maintain mare welfare during breeding.

Cite This Article

APA
Atayde MF, Vidondo B, Bruckmaier R, Freymond SB, Sieme H, Rey-Kaeser R, Burger D. (2025). Cortisol and heart rate response of mares during the in-hand breeding procedure with and without restraint. Equine Vet J. https://doi.org/10.1111/evj.70083

Publication

Equine veterinary journal
ISSN: 2042-3306
NlmUniqueID: 0173320
Country: United States
Language: English

Researcher Affiliations

Atayde, Maria Fernanda
  • Swiss Institute of Equine Medicine, Vetsuisse Faculty University of Bern, Avenches, Switzerland.
Vidondo, Beatriz
  • Veterinary Public Health Institute, University of Bern, Liebefeld, Switzerland.
Bruckmaier, Rupert
  • Veterinary Physiology, Vetsuisse Faculty, University of Bern, Bern, Switzerland.
Freymond, Sabrina Briefer
  • Agroscope, Swiss National Stud Farm, Les Longs-Prés, Avenches, Switzerland.
Sieme, Harald
  • Clinic for Horses - Unit for Reproductive Medicine, University of Veterinary Medicine Hannover, Hannover, Germany.
Rey-Kaeser, Rebekka
  • Swiss Institute of Equine Medicine, Vetsuisse Faculty University of Bern, Avenches, Switzerland.
Burger, Dominik
  • Swiss Institute of Equine Medicine, Vetsuisse Faculty University of Bern, Avenches, Switzerland.

Grant Funding

  • Foundation Pro Pferd, Switzerland

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