Dehydration in racehorses is a common problem, especially in the Gulf countries. Dehydration occurs when there is excessive loss of water in the horse’s body due to sweat from strenuous exercise or systemic problems such as diarrhea. Race horses can lose up to 50 liters of fluid per period of strenuous exercise. Lower intensity exercise results in 5-10 liters of fluid loss through sweat. Dehydration can also occur due to decreased water intake or administration of certain medications, specifically those that result in excessive urination. Electrolyte imbalances coincide with fluid loss. Proper electrolyte balance is essential to help maintain critical function within the horse’s body.
The best way to prevent dehydration is to always provide fresh clean water and to refresh the water anytime the bucket is empty. When horses are in hard work their water intake can easily double or triple. Another way to increase water intake is to provide water by soaking hay or making a sloppy mash of feed by mixing with lots of water. The addition of a salt block, loose salt as a top dressing or a salt supplement will increase water intake as salt stimulates the thirst response.
It is also important to pay attention to the amount of water the horse is consuming. Just because water buckets are hanging in the stall does not mean that the horse will drink. Research has shown that horses prefer water between 7-18°C (45-65°F) or room temperature, especially during the cold months. Some horses will refuse to drink if the bucket is dirty or if offered water at a new location. In this instance, take some water from home or flavor it. For those horses who don’t drink well switch to haylage, which has a higher moisture content. Frequent stops should be made (every 2 to 3 hours) when traveling to offer water to the horse to help prevent dehydration.
Electrolytes also assist the body in maintaining a healthy fluid balance by controlling the horse’s desire to drink. Regular supplementation with a well-formulated electrolyte supplement will return the body’s electrolyte balance to normal after exercise and encourage the horse to drink. Electrolyte preparations can be provided in a separate bucket or top-dressed on feed. A properly balanced electrolyte supplement contains potassium, sodium and chloride at 1:2:4 ratios. Do not use electrolyte preparations with glucose or other sugars listed as one of the main ingredients because excessive sugars can have a negative effect on electrolyte replacement therapy. Horses treated with Furosemide, a diuretic, are more at risk for dehydration and electrolyte imbalances. These horses water and electrolyte consumption should be closely monitored.
In addition to preventing dehydration it is important to recognize signs of dehydration. A dehydrated horse is dull and lethargic, and after exercise is slow to recover to a normal pulse and respiration. Urine may be dark in color and mucous membranes congested and red in appearance. Decreased skin elasticity is a sign of dehydration and can be noted by pinching a fold of skin.