Water and Dehydration Study Clarification

TheHorse.com
by: Multiple Authors

A 2008 Equine Veterinary Journal (EVJ) publication examining dehydration in working horses was summarized and printed onTheHorse.com on April 24, 2008, prior to its actual publication in EVJ. It was reviewed and approved by the researcher. The complete publication (in which Dr. Joy Pritchard was first author) was titled "Validity of indicators of dehydration in working horses: a longitudinal study of changes in skin tent duration, mucous membranes, and drinking behavior."

Recently, Dr. Olin Balch, a member of Veterinary Committee of the American Endurance Ride Conference (AERC) contacted Pritchard and TheHorse.com with committee concerns that the summary could be misinterpreted, especially where endurance horses are concerned.

Balch and Pritchard coauthored the following clarification.

Pritchard said, "My research studied changes in physiological parameters in 50 working horses pulling carts or carrying loads at moderate speeds in Lahore, Pakistan, over a period of 5 hours. While these results could be generalized to similar horses in developing countries, the conclusions are not directly transferable to any other horses, endurance or otherwise.

"The results illustrate that--in the sample population studied--neither a set of standardized skin tent tests, nor gingival mucous membrane dryness, nor other clinical parameters including heart rate, respiratory rate, and coat dryness/wetness were associated with hydration status," she continued. "Only volume of water drunk and drinking behavior were significantly associated with hydration status in these animals.

"The EVJ paper states clearly in the discussion and conclusion that working horses may not drink for internal and external reasons. Lack of drinking is not a conclusive sign of normal hydration status in the animals studied."

Balch said, "As a member of the Veterinary and Research Committees of the AERC, I believe that Dr. Pritchard has written a very important paper emphasizing that classic indicators of dehydration in horses (such as skin tent duration and mucous membrane dryness) may be quite misleading. The AERC sanctions approximately 23,000 horse starts in well-organized, veterinarian-supervised endurance rides in the U.S. and Canada annually.

"It is our collective experience, as experienced endurance veterinarians, that it is extremely common for horses in endurance rides to become dehydrated and yet refuse to drink water," continued Balch. "This is especially common early in rides where an excited horse may travel 25 miles without taking a drink. Additionally, we are convinced that exercising horses who refuse to drink water and become extremely dehydrated run the very real risk of suffering metabolic disorders. That is why riders must be attuned to their horses' water intake and take care to assure their horses are drinking adequately during endurance rides. The consequences of severe ileus or other forms of colic following dehydration and electrolyte depletion, although extremely rare at endurance rides, may lead to death.

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