Endurance horses lose tremendous amounts of electrolytes in sweat during a race. So, it’s not surprising that supplementation of horses with concentrated electrolyte pastes at frequent intervals is a common practice among endurance riders.
Researchers at Oklahoma State undertook a study to determine the effects of this on the horse’s stomach, particularly on gastric ulcer score. There were 14 horses divided into two groups. One group received 2 oz. of water every hour for 8 hours. The other received 2 oz. of concentrated electrolyte paste on the same schedule.
The concentration of individual electrolytes per ounce was: 5528 mg sodium, 11,886 mg chloride, 3657 mg potassium, 754 mg calcium and 153 mg magnesium. Horses had their stomachs scoped before and after the eight-hour period.
There was a significant increase in both the number and severity of gastric ulcers in the horses receiving the concentrated electrolytes, with the authors concluding that frequent dosing of electrolytes could be harmful to the stomach. It should be mentioned here, too, that exercise itself is a risk factor for gastric ulcers, so this schedule of dosing in a horse that is also exercising could pose an even greater risk.
However, you should be able to minimize any potential harm from electrolyte supplementation by one or more of the following modifications of dosing:
Administer electrolytes in drinking water.
Administer concentrated electrolytes immediately after the horse had a chance to drink, preferably a few gallons.
Wait until after the horse has eaten to give electyrolytes.When you must syringe in the electrolytes, using a liquid antacid or corn oil as the carrier for electrolyte powders may help.
Finally, don’t count on signs of colic to alert you that your horse may have gastric ulcers. Nervousness, poor performance, poor eating and drinking during the ride, even poor recovery rates may be nonspecific signs caused by ulcers.
Note: A 2004 University of California study scoped endurance horses at the end of either a 50 or 80 km race and found that 67% had gastric ulcers.