Parturition in horses is dominated by parasympathetic activity of the autonomous nervous system.
Abstract: External and internal stressors prolong parturition in different species. At parturition, sympathoadrenal activation should be avoided because an increased sympathetic tone may cause uterine atonia via β2-receptors. We hypothesized that at physiological parturition, horses are under parasympathetic dominance, and stress-response mechanisms are not activated during delivery of the foal. To evaluate stress responses, heart rate, heart rate variability, catecholamines, and cortisol were analyzed in mares (n = 17) throughout foaling. Heart rate decreased from 2 hours before (51 ± 1 beats/minute) to 2 hours after delivery (41 ± 2 beats/minute; P < 0.05). Heart rate variability variables, standard deviation of the beat-to-beat interval, and root mean square of successive beat-to-beat differences, changed over time (P < 0.05) with the highest values within 15 minutes after delivery. The number of mares with atrioventricular blocks and the number of atrioventricular blocks per mare increased over time (P < 0.01) and were significantly elevated from 15 minutes before to 45 minutes after birth of the foal. Salivary cortisol concentrations increased to a maximum at 30 minutes after delivery (25.0 ± 3.4 ng/mL; P < 0.01). Plasma epinephrine and norepinephrine concentrations showed significant fluctuations from rupture of the allantochorion to expulsion of the fetal membranes (P < 0.01) but were not markedly elevated at any time. In conclusion, mares give birth under high parasympathetic tone. Cortisol release during and after foaling is most likely part of the endocrine pathways regulating parturition and not a labor-associated stress response.
Copyright © 2014 Elsevier Inc. All rights reserved.
Publication Date: 2014-03-27 PubMed ID: 24767599DOI: 10.1016/j.theriogenology.2014.03.015Google Scholar: Lookup
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Summary
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This research paper investigates the influence of nervous system activity on horse parturition, suggesting that natural birth in horses is dominated by parasympathetic activity and stress response mechanisms aren’t typically activated during delivery.
Research Hypothesis and Methods
- The researchers hypothesized that physiological (normal) parturition in horses is under parasympathetic dominance, and stress-response mechanisms are not activated during the birth of the foal.
- They evaluated this by studying heart rate, heart rate variability, catecholamines, and cortisol levels in mares (17 in total) throughout the birthing process.
Key Findings
- Key findings indicate that the heart rate decreased from 2 hours before birth to 2 hours after delivery.
- Other heart rate variables such as the standard deviation of the beat-to-beat interval and the root mean square of successive beat-to-beat differences displayed changes over time, with the highest values recorded 15 minutes after delivery.
- An increase was noted in the number of mares with atrioventricular blocks from 15 minutes before till 45 minutes after birth.
- Salivary cortisol concentrations spiked at 30 minutes after delivery while plasma epinephrine and norepinephrine concentrations displayed significant changes from the rupture of the allantochorion until the expulsion of fetal membranes but were not primarily elevated at any given time.
Conclusion
- The study concludes that mares experience parturition under a high parasympathetic tone.
- The release of cortisol during and after foaling is considered to be part of the endocrine mechanisms regulating parturition rather than a labor-induced stress response.
This study contributes to the understanding of parturition in horses, suggesting that the birthing process is conducted without significant stress or sympathetic activity. It helps comprehend the changes in heart rate and other physiological parameters during labor in mares, impacting the management of equine reproduction health.
Cite This Article
APA
Nagel C, Erber R, Ille N, von Lewinski M, Aurich J, Möstl E, Aurich C.
(2014).
Parturition in horses is dominated by parasympathetic activity of the autonomous nervous system.
Theriogenology, 82(1), 160-168.
https://doi.org/10.1016/j.theriogenology.2014.03.015 Publication
Researcher Affiliations
- Graf Lehndorff Institute for Equine Science, Vienna University of Veterinary Sciences, Neustadt (Dosse), Germany. Electronic address: Christina.Nagel@vetmeduni.ac.at.
- Section for Artificial Insemination and Embryo Transfer, University of Veterinary Sciences, Vienna, Austria.
- Section for Obstetrics and Gynaecology, University of Veterinary Sciences, Vienna, Austria.
- Graf Lehndorff Institute for Equine Science, Vienna University of Veterinary Sciences, Neustadt (Dosse), Germany.
- Section for Obstetrics and Gynaecology, University of Veterinary Sciences, Vienna, Austria.
- Division of Biochemistry, University of Veterinary Sciences, Vienna, Austria.
- Section for Artificial Insemination and Embryo Transfer, University of Veterinary Sciences, Vienna, Austria.
MeSH Terms
- Animals
- Autonomic Pathways
- Epinephrine / blood
- Heart Rate
- Horses / physiology
- Hydrocortisone / metabolism
- Norepinephrine / blood
- Parasympathetic Nervous System / physiology
- Parturition / physiology
- Stress, Physiological
Citations
This article has been cited 7 times.- Erickson EN, Gotlieb N, Pereira LM, Myatt L, Mosquera-Lopez C, Jacobs PG. Predicting labor onset relative to the estimated date of delivery using smart ring physiological data. NPJ Digit Med 2023 Aug 19;6(1):153.
- Felici M, Sgorbini M, Baragli P, Lanatà A, Marmorini P, Camillo F. Autonomic nervous system balance in parturient mares: Spontaneous vs induced delivery. PLoS One 2023;18(3):e0283116.
- Grant AD, Erickson EN. Birth, love, and fear: Physiological networks from pregnancy to parenthood. Compr Psychoneuroendocrinol 2022 Aug;11:100138.
- Martínez-Burnes J, Muns R, Barrios-García H, Villanueva-García D, Domínguez-Oliva A, Mota-Rojas D. Parturition in Mammals: Animal Models, Pain and Distress. Animals (Basel) 2021 Oct 14;11(10).
- Nagel C, Melchert M, Aurich C, Aurich J. Differences in Endocrine and Cardiac Changes in Mares and Her Fetus before, during, and after Parturition in Horses of Different Size. Animals (Basel) 2020 Sep 4;10(9).
- Gonçalves H, Pinto P, Silva M, Ayres-de-Campos D, Bernardes J. Electrocardiography versus photoplethysmography in assessment of maternal heart rate variability during labor. Springerplus 2016;5(1):1079.
- Narazaki T, Mori M, Matsuzawa Y, Saito A, Kinoshita C, Kurita M, Matsumiya K, Okada H, Sakamoto KQ. Apparent reduction in heart rate during oviposition revealed by non-invasive heart rate monitoring of gravid loggerhead turtles. Front Physiol 2025;16:1540252.
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