by Tamara Baysinger
As conditioning rides get longer and competition days loom, distance riders focus more than ever on ensuring their horses' welfare. The inextricably linked factors of hydration and electrolytes are key to success.
This article will explore the interplay of hydration and electrolytes in distance horses. We’ll consider why fluids are lost and how electrolytes are relevant to hydration. We will also cover steps riders can take to minimize losses and replace water and electrolytes in their hard-working horses.
Equine athletes generate an astonishing amount of heat. Susan Garlinghouse, DVM, observed in a 2000 Endurance News article that "During a fifty-mile ride in ambient temperatures, the average horse will produce enough heat to melt a 150-pound block of ice, and then bring that water to a boil."
The distance horse’s welfare depends on his ability to efficiently shed all that heat. Horses cool themselves primarily through respiration and sweating. Dr. Garlinghouse notes that a horse working in hot conditions can lose 1.5 to 4 gallons of sweat per hour. All that water comes from fluid stored within cells, between cells, and in the digestive tract.
Dehydration causes the blood to thicken, which results in reduced blood flow to the cooling network of blood vessels in the skin, as well as muscle fatigue. Additionally, a horse’s pH becomes more alkaline during protracted exercise, potentially leading to symptoms such as disrupted nerve signaling (perhaps resulting in clumsiness or “thumps”), muscle cramps, irregular heartbeat, and gut malfunction (Nancy Loving, DVM, All Horse Systems Go).
Critically, experts including Dr. Garlinghouse and Dr. Harold Schott of Michigan State University point out, as a horse sweats his rate of electrolyte loss keeps pace with his rate of fluid loss. This means that sweating doesn't result in in the increased concentration of sodium in the bloodstream that is necessary to trigger the thirst response. As a result, the horse can be quite dehydrated but fail to show interest in drinking.
Minimizing Fluid and Electrolyte Losses in the Working Horse
The first step to minimizing fluid and electrolyte losses begins long before competition day, with your conditioning program. Nancy Loving, DVM, notes in her book Going the Distance that as a horse gains fitness, his network of blood vessels and capillary beds expands. This allows more blood to be carried to the surface for cooling. Additionally, an overweight horse that leans out during conditioning has less insulation to trap heat.
The horse’s diet also contributes to his ability to stay cool and hydrated. A gut full of forage holds about 20 gallons of fluid, much of which can be transferred to the bloodstream when needed. For this reason, maximizing forage intake in the days prior to a challenging ride is particularly important. Choosing grass hay over alfalfa will cause the horse to generate less internal heat during the digestive process.
There has been much discussion in the distance riding community regarding whether horses should be pre-dosed with electrolytes before an event. Dr. Garlinghouse points out that while supplementing with additional electrolytes for days in advance of a ride is unnecessary, as the excess will simply be excreted in urine, providing small doses early and often on race day helps encourage drinking and prevent depletion (Endurance News, 2000).
Replacing Fluid and Electrolytes during Competition
During a distance event, especially in hot or humid conditions, it is not possible to fully replace all the fluid and electrolytes your horse is bound to lose. However, steps can be taken to support him with partial replenishment that is sufficient to complete the mileage safely.
The first step to is to adjust your ride plan to the conditions. Heat obviously causes a horse to sweat more. Humidity can reduce the cooling benefits of sweat dramatically, even serving as insulation if the air is still. A horse that is still shedding out his winter coat may struggle on an unseasonably warm, spring day. It may be wise to ride slower than planned in order to ensure your horse’s welfare.
Dr. Garlinghouse emphasizes that it is always best to supplement electrolytes before a horse becomes dehydrated and after he has consumed water. Concerning timing of electrolyte administration, Dr. Loving notes that orally administered electrolytes take 1-2 hours to enter the bloodstream.
Research by Dr. Schott and his team at Michigan State University demonstrates that horses go on to drink more overall if they consume water containing electrolytes before consuming plain water. During holds, you can offer water with a dose of electrolytes mixed in. It is generally recommended to offer plain water as well, in case the horse refuses the saltier option.
Some horses will eat electrolytes mixed into a sloppy mash. If your horse won’t eat or drink his electrolytes, and must be dosed with a syringe, it is best to wait until after he has consumed feed and water so you don’t accidentally curb his appetite. In order to protect sensitive stomach tissues from ulcer formation or upset, many riders offer a bit of alfalfa or some antacid (without bicarbonate as an ingredient) as a buffering agent alongside electrolytes.
After a long-distance effort, a horse that is eating and drinking well may benefit from continued electrolyte supplementation for a day or so to help him recover. Exhausted or dehydrated horses, however, should be evaluated by the vet before dosing.
Establishing an exact protocol ~ which product should be given, how much, and how often to a particular individual on any given day ~ is an art and science sufficient to challenge any horseman for a lifetime. If you’re a beginner, don’t hesitate to reach out to the vet, your mentor, or more experienced riders for advice.
At the end of the day, it all comes down to understanding what is going on under the hood. Observe your horse carefully throughout the ride. When in doubt, slow down and give him a chance to graze. And remember, to finish is to win.
Top 5 Book Recommendations for Distance Riders
The Sweaty Equestrian