New Method for Scoring Sweat Losses in Horses Proposed

Warm summer weather is just around the corner, which means many owners will be hosing sweaty horses after exercise on a regular basis. But how much sweat are you rinsing down the drain after each ride? The National Research Council and German Society for Nutrition Physiology's current estimation methods depend on the amount of work the horse performs, but a group of researchers from Germany and the United Kingdom have proposed a new scoring system to measure sweat loss in exercised horses.

“We’ve performed a number of studies on the effects of sodium chloride on the acid, base, and mineral status in sport horses, and as a result, we are aware of the high importance of exact data on electrolyte supply and, thus, on sweat losses,” relayed Annette Zeyner, a professor of animal nutrition at Martin Luther University in Halle-Wittenberg, Germany.

Zenyer and colleagues hypothesized that scoring equine sweat loss via specific, externally visible characteristics would be more practical and accurate than current estimation methods. The team employed 17 Warmblood-type mares that participated in two separate exercise regimens on consecutive summer days:

  • Light Work: 10 minutes fast walk, 10 minutes trot, 5 minutes canter, 5 minutes trot, and 10 minutes slow walk; and
  • Medium Work: 15 minutes fast walk, 10 minutes trot, 10 minutes canter (including some gallop), 5 minutes trot, 10 minutes canter, and 10 minutes slow walk.

The team groomed and weighed the horses before exercise and three hours after exercise to determine body weight losses, which they corrected for water intake, fecal and urinary output, and estimated respiratory water losses. Immediately after completing each exercise regimen, they unsaddled and photographed the horses to record sweat patterns.

Upon reviewing their study results, the researchers noted five distinct sweating patterns, which were each directly associated with a defined sweat loss range according to body weight losses. Using this data, they devised the following sweat loss scoring system:

Sweat Score Phenotypic (Observable) Peculiarities Sweat losses determined in the study
1 Area under the saddle partly dry, but partly dark, sticky, and moist; sticky throat area; flanks darker than normal 1 – 4 liters
(0.2 – 0.7% of body weight)
2 Wet area under the saddle and on the throat; small white areas at the edges of the saddle corners may occur through foaming friction surfaces between throat and reins as well as on the posterior; inner limbs (with heavily muscled or fat horses) may be white-colored due to foaming > 4 – 7 liters
(> 0.7 – 1.2% of body weight)
3 Snaffle leaves a clear wet impression on the head (often with foam on the back piece and noseband); throat and areas under saddle and girth consistently wet; flanks clearly wet > 7 – 9 liters
(> 1.2 – 1.5% of body weight)
4 Throat and flanks completely wet; moist, dark wrinkles above the eyes; in heavily muscled or fat horses white-colored between posterior inner limbs because of pronounced foaming > 9 – 12 liters
(> 1.5 – 2% of body weight)
5 Horses additionally dripping fluid above the eyes and under the belly > 12 – 18 liters
(> 2 – 3% of body weight)

“Other important factors which are difficult to quantify (e.g., athletic fitness, climatic adaptation, hair length, etc.) can also have significant influence on sweat losses,” the team noted.

They believe their proposed scoring system to be more accurate than other methods because it takes these factors into account, but added, “further studies are required to verify the score proposed here and to check it can be applied to other conditions.”

The study, “Scoring of sweat losses in exercised horses—a pilot study,” will appear in an upcoming issue of Journal of Animal Physiology and Animal Nutrition

Disclaimer: Seek the advice of a qualified veterinarian before proceeding with any diagnosis, treatment, or therapy.