Next Article in Journal
Salmonid Jumping and Playing: Potential Cultural and Welfare Implications
Previous Article in Journal
A Decade of Progress toward Ending the Intensive Confinement of Farm Animals in the United States
Article Menu

Export Article

Open AccessReview
Animals 2017, 7(6), 41; doi:10.3390/ani7060041

Equine Welfare during Exercise: An Evaluation of Breathing, Breathlessness and Bridles

Animal Welfare Science and Bioethics Centre, Institute of Veterinary, Animal and Biomedical Science, College of Sciences, Massey University, Palmerston North 4442, New Zealand
*
Author to whom correspondence should be addressed.
Academic Editor: Marina von Keyserlingk
Received: 28 March 2017 / Revised: 22 May 2017 / Accepted: 23 May 2017 / Published: 26 May 2017
View Full-Text   |   Download PDF [1505 KB, uploaded 26 May 2017]   |  

Abstract

Horses engaged in strenuous exercise display physiological responses that approach the upper functional limits of key organ systems, in particular their cardiorespiratory systems. Maximum athletic performance is therefore vulnerable to factors that diminish these functional capacities, and such impairment might also lead to horses experiencing unpleasant respiratory sensations, i.e., breathlessness. The aim of this review is to use existing literature on equine cardiorespiratory physiology and athletic performance to evaluate the potential for various types of breathlessness to occur in exercising horses. In addition, we investigate the influence of management factors such as rein and bit use and of respiratory pathology on the likelihood and intensity of equine breathlessness occurring during exercise. In ridden horses, rein use that reduces the jowl angle, sometimes markedly, and conditions that partially obstruct the nasopharynx and/or larynx, impair airflow in the upper respiratory tract and lead to increased flow resistance. The associated upper airway pressure changes, transmitted to the lower airways, may have pathophysiological sequelae in the alveolae, which, in their turn, may increase airflow resistance in the lower airways and impede respiratory gas exchange. Other sequelae include decreases in respiratory minute volume and worsening of the hypoxaemia, hypercapnia and acidaemia commonly observed in healthy horses during strenuous exercise. These and other factors are implicated in the potential for ridden horses to experience three forms of breathlessness—”unpleasant respiratory effort”, “air hunger” and “chest tightness”—which arise when there is a mismatch between a heightened ventilatory drive and the adequacy of the respiratory response. It is not known to what extent, if at all, such mismatches would occur in strenuously exercising horses unhampered by low jowl angles or by pathophysiological changes at any level of the respiratory tract. However, different combinations of the three types of breathlessness seem much more likely to occur when pathophysiological conditions significantly reduce maximal athletic performance. Finally, most horses exhibit clear behavioural evidence of aversion to a bit in their mouths, varying from the bit being a mild irritant to very painful. This in itself is a significant animal welfare issue that should be addressed. A further major point is the potential for bits to disrupt the maintenance of negative pressure in the oropharynx, which apparently acts to prevent the soft palate from rising and obstructing the nasopharynx. The untoward respiratory outcomes and poor athletic performance due to this and other obstructions are well established, and suggest the potential for affected animals to experience significant intensities of breathlessness. Bitless bridle use may reduce or eliminate such effects. However, direct comparisons of the cardiorespiratory dynamics and the extent of any respiratory pathophysiology in horses wearing bitted and bitless bridles have not been conducted. Such studies would be helpful in confirming, or otherwise, the claimed potential benefits of bitless bridle use. View Full-Text
Keywords: horse; equine welfare; breathing during exercise; jowl angle; soft palate displacement; lower airway pathophysiology; breathlessness; dyspnoea; bit problems; bitless bridle impacts horse; equine welfare; breathing during exercise; jowl angle; soft palate displacement; lower airway pathophysiology; breathlessness; dyspnoea; bit problems; bitless bridle impacts
Figures

Figure 1

This is an open access article distributed under the Creative Commons Attribution License which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. (CC BY 4.0).

Scifeed alert for new publications

Never miss any articles matching your research from any publisher
  • Get alerts for new papers matching your research
  • Find out the new papers from selected authors
  • Updated daily for 49'000+ journals and 6000+ publishers
  • Define your Scifeed now

SciFeed Share & Cite This Article

MDPI and ACS Style

Mellor, D.J.; Beausoleil, N.J. Equine Welfare during Exercise: An Evaluation of Breathing, Breathlessness and Bridles. Animals 2017, 7, 41.

Show more citation formats Show less citations formats

Note that from the first issue of 2016, MDPI journals use article numbers instead of page numbers. See further details here.

Related Articles

Article Metrics

Article Access Statistics

1

Comments

[Return to top]
Animals EISSN 2076-2615 Published by MDPI AG, Basel, Switzerland RSS E-Mail Table of Contents Alert
Back to Top