Can a Horse Consume Too Many Electrolytes?
Q. My horse usually does not drink well when stalled, but she seems to prefer water with electrolytes. When given both a bucket of 5 gallons of water mixed with a scoop of electrolytes and one with plain water, she’ll only drink the electrolyte water. Is it possible for her to consume too many electrolytes if that’s all she’s drinking when stalled on cold nights? She’s getting a ration balancer, which should cover all her mineral needs, so does she need additional electrolytes?

A. Keeping horses hydrated in cold weather is so important and is often a challenge. It sounds as though you might have found a great solution to ensure your mare will drink when she’s stabled. In addition to just drinking more water, you mare might need the electrolytes you’re putting in the water.

While ration balancers do a fabulous job of delivering the majority of a horse’s mineral and vitamin needs, they don’t always provide enough sodium and chloride to meet electrolyte needs, especially if a horse is in work. This is also true of other types of commercial feeds even when properly fed. In comparing four popular ration balancers I found the amount of sodium provided by feeding 1.5 pounds per day (a typical feeding rate) varies from 3.4 grams to 8.8 grams.

According to the National Research Council’s Nutrient Requirements of Horses, a 1,200-pound horse in light work requires 15.1 grams of sodium a day and 50.8 grams of chloride. Based on the amount of sodium in the ration balancers, forage needs to contribute a considerable amount of sodium if sources are available.

Levels of sodium in forage also vary greatly. According to Equi-Analytical’s database of grass hay analyses, the average sodium content based on more than 43,000 samples is 0.068% with a range of 0 (too little to register on the test) to 0.209%. If we assume that the same 1,200-pound horse is consuming 1.5% of its body weight in hay (18 pounds) with a 0.068% sodium concentration, the hay would provide 5.6 grams of sodium. Even at the upper end of the range of sodium provided by the ration balancers I surveyed, the total amount of sodium the horse consumes wouldn’t meet his daily requirements.

Of course, your horse might very well be eating more hay then this, and your hay might have higher sodium levels, so perhaps daily electrolyte needs are being met. However, unless you’re testing your hay and weighing how much you’re feeding, you just do not know. Therefore, it’s quite possible that despite feeding a ration balancer your mare needs additional electrolytes. This might be part of the reason she so readily drinks water with added electrolytes. Of course, she might also have like the taste.

One scoop of electrolyte is typically 1 to 2 ounces depending on the scoop size and product density. A serving of a good electrolyte will typically have sodium or salt as the first ingredient and provide over 6 grams of sodium and 12 grams of chloride per serving. Providing this on a daily basis can go a long way to making sure a horse’s electrolyte needs, especially sodium, are being met.

The concentration of sodium in the blood contributes to your horse’s desire to drink. Low circulating sodium results in lower thirst and vice versa. So, ensuring adequate sodium in the diet is crucial to hydration. While your concern appears to be in getting her to drink when you bring her in, it might also be an issue when she is out. You just can’t tell so easily how much she is drinking when she’s out.

The amount of electrolyte you provided in the 5-gallon bucket isn’t enough to cause concern. As long as adequate water is available and the horse isn’t obviously dehydrated and has good kidney function, consuming even relatively large amounts of electrolytes isn’t an issue. If it’s more than needed, the horse will drink more water.

Feeding table salt is another easy and cost-effective way to get sodium and chloride into your horse daily (2 tablespoons per 500 pounds of body weight). You can save your electrolytes for days when you need to replace sweat loss, which is their proper purpose. However, if your horse doesn’t like to eat salt or you prefer to feed an electrolyte every day, it’s certainly okay to do. The key is that your mare is consuming her daily requirement so she keeps drinking, whether she’s in her stall or on pasture.