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Home / Equine Research Bank / J Equine Vet Sci / Circadian and Circannual Regulation in the Horse: Internal T...
Journal of equine veterinary science2019; 76; 14-24; doi: 10.1016/j.jevs.2019.02.026

Circadian and Circannual Regulation in the Horse: Internal Timing in an Elite Athlete.

Abstract: Biological rhythms evolved to provide temporal coordination across all tissues and organs and allow synchronization of physiology with predictable environmental cycles. Most important of these are circadian and circannual rhythms, primarily regulated via photoperiod signals from the retina. Understanding the nature of physiological rhythms in horses is crucially important for equine management. Predominantly, they have been removed from exposure to their natural environmental stimuli; the seasonally changing photoperiod, continuous foraging and feeding activity, social herd interactions, and the continuous low-intensity exercise of a grassland dweller. These have been replaced in many cases with confined indoor housing, regimental feeding and exercise times, social isolation, and exposure to lighting that is often erratic and does not come close to mimicking the spectral composition of sunlight. Man has further altered seasonal timing cues through the use of artificial lighting programs that impact reproductive behavior, breeding efficiency, and the development of youngstock. Understanding how these new environmental cues (some stronger and some weaker) impact the internal physiology of the horse in the context of the natural endogenous rhythms that evolved over millennia is key to helping to improve equine health, welfare, and performance, now and into the future. This review provides an overview of the field, highlights the recent discoveries related to biological timing in horses, and discusses the implications that these findings may have for the production and management of the elite equine athlete.
Copyright © 2019 Elsevier Inc. All rights reserved.
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Publication Date: 2019-03-07 PubMed ID: 31084748DOI: 10.1016/j.jevs.2019.02.026Google 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.

This paper examines how natural rhythms in horses, most notably their daily (circadian) and annual (circannual) cycles, are significantly influenced by both their environment and man-made alterations to it. It also looks at how understanding these natural rhythms and changes can influence horse health and performance.

Introduction to Biological Rhythms in Horses

  • The circadian and circannual rhythms in horses are fundamental biological systems. They evolved to coordinate all tissues and organs and synchronize the physiology of the animal with predictable environmental cycles, such as daylight and seasons.

Nature of Physiological Rhythms in Horses

  • The primary regulator of these rhythms is signals from the retina correlating with photoperiod, or the duration of an organism’s daily exposure to light.
  • It is paramount to understand these rhythms, as they play a vital role in equine management.

Changes in Horses’ Environment

  • Over time, horses have largely been removed from their natural stimuli, including continuous foraging, social herd interactions, and consistent low-intensity exercise. These have largely been replaced with man-made routines and conditions such as indoor housing and scheduled feeding and exercise times.
  • Notably, modern horses’ exposure to light, a key element in the regulation of their natural rhythms, has changed. They are now often exposed to erratic light schedules and light sources that do not mimic the spectral composition of sunlight.

Humans’ Impact on Horses’ Behaviour and Well-being

  • Human interventions, such as the use of artificial lighting programs, have also significantly impacted horses’ behavior, particularly when it comes to their seasonal timing cues. This has consequences on reproductive behaviour, breeding efficiency, and the development of young horses.
  • Understanding the effects that these newer environmental cues (some of which are stronger than others) have on horses’ internal physiology is essential when looking at how they now interact with their natural endogenous rhythms that evolved over many millennia.

Application to the Equine Industry

  • This understanding is key for improving equine health, welfare, and performance in the present and the future.
  • The review provides an overview of the discipline, shines a light on recent discoveries relating to biological timing in horses, and discusses the implications these findings could have on the production and management of exceptional equine athletes.

Cite This Article

APA
Murphy BA. (2019). Circadian and Circannual Regulation in the Horse: Internal Timing in an Elite Athlete. J Equine Vet Sci, 76, 14-24. https://doi.org/10.1016/j.jevs.2019.02.026

Publication

Journal of equine veterinary science
ISSN: 0737-0806
NlmUniqueID: 8216840
Country: United States
Language: English
Volume: 76
Pages: 14-24

Researcher Affiliations

Murphy, Barbara A
  • School of Agriculture and Food Science, University College Dublin, Dublin, Ireland. Electronic address: Barbara.murphy@ucd.ie.

MeSH Terms

  • Animals
  • Athletes
  • Horses
  • Humans
  • Light
  • Male
  • Periodicity
  • Photoperiod
  • Physical Conditioning, Animal

Citations

This article has been cited 22 times.
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