by Peter Waller

Created on: February 20, 2007   Last Updated: June 25, 2009

When we ask our horse to perform, it depends on the level of exercise it gets as to how much actual bodyweight it will lose in the form of sweat. There are other extenuating circumstances that will also contribute to this loss; such as the ambient temperature and humidity and losses through urination due to the need to excrete urea formed from the detoxification of ammonia produced through the deanimation of amino acids during exercise.

We as riders of these horses should be aware of the state of the hydration of these horses - there was an instance about 12 months ago where there was a clinic being held during one of the hottest months we have experienced for years and as a consequence of the attendees being under the instruction of a visiting overseas Olympic rider and trying to gain a place in the Queensland squad, pushed these horses without a drink for quite a period of time - the result was not favorable for the horses. One was lost, one got to such a state of dehydration and electrolyte loss it went off its head and went through a rail and badly injured itself, and it was reported that at least 4 other horses were hospitalized in an attempt to rehydrate them.... leaves a lot to be desired as to the horsemanship skills of this visiting rider I think.

Back to the subject at hand however -

There are three stages of dehydration;
mild; (up to 3% bodyweight loss) - signs are a decrease in urinary output and a slight decrease in skin elasticity.

moderate; (5% bodyweight loss) - there is a marked skin elasticity loss, shrunken eyes, weakness and a weak pulse rate.

severe; (10% bodyweight loss)- sever dehydration presents quite markedly, it includes circulatory failure, infrequent dry feces, and
a severe electrolyte imbalance.

These severely dehydrated horses may not want to drink and affected horses may have lost so much electrolyte from their system that their blood becomes more dilute than usual and this triggers a mechanism in an area of the brain (hypothalamus) that switches on and the horse fails to recognize it is in fact thirsty, and no amount of coaxing will get these horses to drink and the only hope of saving the horse from this predicament is to place it on an IV electrolyte drip or stomach tube with an electrolyte balancer it to rehydrate it until this trigger mechanism switches off (5-10lt every 30-60 minutes) and the horse begins to drink volunantarily.
These horses lose not only water, but sodium, postassium, chloride, and urea when they sweat, and it could take up to a week of normal feeding in order to replace these electrolyte losses.
Everyone knows that the most common test to see if your horse needs hydration is to take a pinch of skin between the forefinger and thub. I have seen many people do this, howver, they do the 'pinch test' on the neck area. This test is more effective and accurate if you do this pinch test on the ribcage than on the neck.

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