During training a horse’s body temperature rises very quickly, and the process is much more intense than in people. The horse starts to sweat sooner and more heavily, which increases the risk of dehydration. In addition, a reduced sense of thirst is often seen after physical work, because a lower concentration of electrolytes in the blood weakens the mechanisms that regulate water intake.
The risk of dehydration rises clearly as the temperature of the surroundings rises, during transport, at competitions or in stressful situations. Particular attention should be paid to in-foal and nursing mares and to young horses, which are more susceptible to disturbances of water and electrolyte balance. One simple way to assess hydration is to look at skin elasticity. The longer a skin tent takes to return to its original position, the greater the risk of dehydration. Further signs can include a lack of energy, a reduced appetite, dry droppings, sunken eyes and muscle cramps.
From a nutritional point of view, the right amount of dietary fibre plays a key role in preventing dehydration. The horse’s large intestine acts as a natural store of water, but it only works properly if there is constant access to forage, above all hay. Too much starch in the diet, coming from concentrates, can disturb the use of water in the digestive tract, because starch lingering there limits fluid absorption in the large intestine. For that reason, in summer it is worth limiting high-starch feeds and topping up the ration with chaff, vegetable oils or high-fibre grass nuts.
Remember that dehydration is not only a loss of water, but also of electrolytes such as sodium, chloride, potassium and magnesium, which the horse loses in sweat. Constant access to a salt lick is important, but often not enough, because many horses stop using it once the salty taste has satisfied them. The safest and most effective solution is ready-made electrolyte mixes, which contain the full set of essential minerals and additions that aid absorption, such as dextrose. Electrolytes are best given after work, once the vital signs have returned to normal. Because of the salty taste they are often taken more willingly as a mash, which also increases the amount of fluid in the diet.
To sum up, protecting a horse from dehydration should be part of everyday, considered care, not only a reaction to intensive training or high temperatures. A properly balanced diet, based on feeds rich in fibre, constant access to fresh water and regular replacement of electrolytes make it possible to support healthy hydration and, through that, the health and fitness of your horse. And most importantly, remember that water and electrolytes cannot be stored up in advance!