Contribution of respiratory heat loss to heat balance in Thoroughbred horses performing near maximal exercise under thermoneutral and hot-humid conditions

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dc.contributor.advisor Meintjes, R. en
dc.contributor.advisor Guthrie, Alan John en
dc.contributor.postgraduate Lund, Raymond John en
dc.date.accessioned 2013-09-07T13:35:55Z
dc.date.available 2010-10-06 en
dc.date.available 2013-09-07T13:35:55Z
dc.date.created 2001-04-01 en
dc.date.issued 2010-10-06 en
dc.date.submitted 2010-10-06 en
dc.description Thesis (DPhil)--University of Pretoria, 2000. en
dc.description.abstract The purpose of the studies presented in this thesis was to develop a greater understanding of the contribution of respiratory heat loss to the thermal balance of exercising horses. In the first experiment the effect of three different warm-up regimens on the thermal balance of Thoroughbred horses was investigated. The experiments showed that a low intensity warm-up was most beneficial aiding heat dissipation during subsequent exercise. The study also showed the heat loss by sweating is not restricted by the rate of sweat production, but by the evaporation rate of the sweat. In the second experiment, horses were exercised to fatigue in thermoneutral and hot-humid environments. The evaporative heat dissipation from sweating and from the respiratory tract was severely impaired during the hot humid exercise protocol. There was a significant increase in the heart rate and the metabolic rate during the hot humid protocol, thus indicating the additional work done by the horse in an effort to dissipate the rapidly accumulating heat. The significantly shorter time to fatigue may be a mechanism to protect the horse from circulatory collapse as the circulatory demands for cardiac output exceed its capacity. In the third experiment adaptations that the horse is able to make to alleviate the compromised evaporative heat loss were identified. These experiments showed that the horse is able to shorten its stride, increase minute ventilation and the velocity of the air in the conducting airways. The results presented also indicate that the horse is able to modify the evaporative area of the airways to enhance evaporative heat loss from the respiratory tract. The experiments also showed that during exercise in hot-humid environments, small changes in the evaporating surface vapour pressure have a significant effect on the vapour pressure gradient thus having a significant effect on the evaporating heat loss. Finally, the lessons gained during the experiments presented in this thesis were used to revise and refine a mathematical model of the thermal balance of exercising horses. The resulting model is more accurate and easier to apply to use in the field. en
dc.description.availability unrestricted en
dc.description.department Equine Research Centre en
dc.identifier.citation Lund, RJ 2000, Contribution of respiratory heat loss to heat balance in thoroughbred horses performing near maximal exercise under thermoneutral and hot-humid conditions, DPhil thesis, University of Pretoria, Pretoria, viewed yymmdd < http://upetd.up.ac.za/thesis/available/etd-10062010-120524/ en
dc.identifier.other H1122/ag en
dc.identifier.upetdurl http://upetd.up.ac.za/thesis/available/etd-10062010-120524/ en
dc.identifier.uri http://hdl.handle.net/2263/28473
dc.language.iso en
dc.publisher University of Pretoria en_ZA
dc.rights © 2000 University of Pretoria. All rights reserved. The copyright in this work vests in the University of Pretoria. No part of this work may be reproduced or transmitted in any form or by any means, without the prior written permission of the University of Pretoria. en
dc.subject Respiratory heat loss en
dc.subject Horses en
dc.subject UCTD en_US
dc.subject Exercises en_ZA
dc.title Contribution of respiratory heat loss to heat balance in Thoroughbred horses performing near maximal exercise under thermoneutral and hot-humid conditions en
dc.type Thesis en


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