Horse Nutrition During the Warm Season


The best thing about being human is that we are not burdened much with our own nutrition. We eat what we want with a guarantee that we get enough nutrition from our everyday foods. Our equine friends, on the other hand, cannot eat whatever they want as they are dependent on their owners and caretakers to provide them with the proper horse nutrition, the foods that they need to stay healthy.

This, horse nutrition, is then the challenge for us horse care providers, owners, and horse enthusiasts, to understand horse nutrition in relation to providing specific and appropriate feed to our horses. Especially if we put into consideration the stifling summer heat that we are experiencing now. We owe it to our companions to provide proper care and horse nutrition, including access to quality food and water.

There are two major concerns for our horses during the summer season: dehydration and weight loss. We are going to emphasize the importance of water intake and electrolytes during this summer and explain the importance of switching to feeding more readily available sources of forage or supplements with other types of feeds.


Like humans, a horse’s body weight is made up of 60-70% water. That said, our horses need to drink about 10-20 gallons of water a day to keep their bodies working in good condition. And even more during a hot climate ( Kentucky Equine Research ). Hence providing fresh water for our horses is vital.

Horses normally get their water in two different ways. First and foremost in horse nutrition is the water that we provide them, second is the water contained in their feed, which is extracted internally as they break down carbohydrates, proteins, and fats during digestion. Some horses artificially increase the water content of their feeds by soaking or dunking their hay in the water. Although a bit messy, the added benefit of increasing water intake is certainly achieved. Now consider what happens when our equines are sweating excessively due to the hot weather and they refuse to drink the needed water despite the heat. This may just lead to our horses’ dehydration.

Dehydration occurs when a horse does not have enough water in its body to carry out normal functions. And according to Kentucky Equine Research, the horse may lose interest in drinking even when dehydrated because when both water and electrolytes are lost, the physiological trigger that tells a horse when to drink malfunctions.

However, not all thirsty and sweaty horses would be an unmistakable sign of dehydration. On the other hand, the lack of sweat or a resting horse standing in the corner of the paddock showing disinterest does not exactly say hydrated. That said, how could we even tell when our horses are already dehydrated? The most accurate method to determine if your horse is dehydrated is through a complete blood chemistry analysis. The most accurate yet perhaps not the most available, especially if we horse owners and caretakers do not have immediate access to a complete blood chemistry analysis. In this case, there are simple ways, according to Kentucky Performance Products, that we can do in order to check if our dear equines are not experiencing excess loss in fluids. 


– pinching the skin near the point of your horse’s shoulder and pulling it upward into a tent-like shape; that is why it is also called skin tenting and then releasing it. Hydrated horse skin should flatten out within one second after you let it go. If it takes longer than 4 seconds for the skin to snap back, your horse may be dehydrated and need immediate attention.


– can be a cause or a symptom of dehydration. A horse’s average body temperature varies between 98 to 101 degrees. And you can check your horse’s temperature with a rectal thermometer. And it is recommended that you check your horse’s temperature at least once a month to have a baseline body temperature.


– refers to the normal time it takes for the capillaries to refill. One way of doing this is to check on the horse’s gums, by pressing a finger or thumb on your horse’s upper gums for a second or two. If your horse is healthy and well-hydrated their gums should be pink and moist and when you remove your fingers the pressure points will be a lighter color. And if the color returns within one or two seconds, your horse is properly hydrated. If it takes longer, your horse is likely dehydrated.


– when you approach your horse and you notice that your usually joyful horse is showing disinterest while standing still in his paddock speaks that something is amiss. It might be dehydration! Take preventive action immediately and offer your horse water and electrolytes.


– is an indicator of an animal’s general level of hydration and under normal conditions is moist and protected by the secreted viscous mucus from the horse’s conjunctival sac. But when a horse is dehydrated, its eyes become dull, dry, and may look as though they are sunken into its skull.


– urine color is one of the best signs of a horse’s hydration level, clear urine indicates a well-hydrated animal and darker urine means it’s dehydrated. This is because when a horse is dehydrated their kidneys start retaining water. Therefore, less water is released in their urine leading to it being more concentrated and darker.


– typical horses in decent shape have a resting heart rate between 36-42 beats per minute. And when a horse becomes dehydrated they often display a rapid heart rate. A resting heart rate of over 60 could be a sign of dehydration. Hence it is good sense and practice to have a general idea of your horse’s standard resting heart rate.


– In a severely dehydrated horse, blood volume and blood pressure decrease, and sufficient levels of oxygen are not delivered to the brain leading to dizziness and disorientation.

And most importantly in horse nutrition, to be able to have a baseline of what your horse’s normal response looks like, it is a good idea to practice these tests when you know that your horse is properly hydrated.


In cases of severe dehydration, a visit to the vet is of utmost importance and IV treatment administration may be in order. However, in cases of mild dehydration, it can be easily reversed by giving your animal water and some electrolytes. And one simple and primary electrolyte supplement is sodium chloride (salt). According to Thunes (2021) of the Horse Nutrition Commentary Series, horses should always have salt available not just during hot weather/summer season.

The idea is to give your horse a salt block or spray the hay with salt water to encourage your horse to drink more. However, there are many forms of sodium chloride such as plain white blocks, red mineralized blocks to lose forms, iodized, sea salt, kosher salt, Himalayan, and others, and it is therefore important to take into consideration your horse’s preference as not many horses actively use block salt.

With horse nutrition, a 500-kilogram (1,100-pound) horse at maintenance on a cool day needs the amount of sodium provided by about 28 grams (1 ounce or 2 U.S. Tablespoons) of sodium chloride. This equates to just under a kilogram or 2 pounds of salt a month, ( Thunes, 2021 ). If your horse is already readily consuming an appropriate amount of electrolyte supplements (such as after adding water with sodium chloride into their feed) and they are still dehydrated or eating poorly, perhaps due to the extreme weather conditions or suffering from chronic illness, another electrolyte supplement may be warranted. In this case, it is best to approach your veterinarian for any other electrolyte recommendation.

Here is what we agree to be practical guidelines for choosing an electrolyte supplement, from Dr. Oke (2020) on Horse Care, Nutrition, and Other Supplements:

  • Apart from looking into supplements produced by the FDA’s Current Good Manufacturing Practices, which regulate factors such as the purity of ingredients, quality management systems, and operating procedure, another important way to verify standards of quality is to look for a seal on the label that says National Animal Supplement Council (NASC). When you see the Quality Seal on a product, you can trust it comes from a reputable company that has successfully passed an independent quality audit.
  • It is also important to note the clinical research and test that the product went through for safety and efficacy with results published in a peer-reviewed journal.
  • After reading through the labels and you find that you cannot understand what is in the product, even after researching it over on the internet, or what levels of ingredients are inside without having to use a calculator, you should be concerned.
  • Of course, we will have to watch out for the unrealistic claims about speedy results. Like when it says it can cure something, that is a sure sign that the product cannot be trusted.
  • Then, let us not forget about the higher and higher levels of active ingredients. Do not be fooled by this as horses can assimilate only so much. The rest of the ingredients will be wasted as will the extra money that you are paying for the higher dose.


Apart from dehydration, you may also witness weight loss.  Forages and pasture grasses are typically the main source of energy (protein, fat, and carbohydrates) and are digested by a process that requires fermentation; this process generates heat which can also compound any underlying issues with decreased food consumption and dehydration. This then poses a problem, not just associated with weight loss but also with the horse’s capacity to internally absorb water. When there is no proper intake of forage, to begin with, there is an added deficit to the water consumption and absorption. We believe that we only need one rule for horse nutrition and feeding: Keep it simple.

During the summer season with temperatures rising, horses will commonly be eating less. Even the staple diet of hay or pasture is consumed at a slower rate. As previously mentioned, this problem may be compounded by the heat that is generated from the forage during fermentation.

Also, even when sitting in the feeder for just a few hours, daily horse feed like hay may experience secondary fermentation due to continued bacterial growth because of high heat. Secondary fermentation causes a reduction of feed quality, generates undesirable odors, and may result in reduced intake ( Kentucky Equine Research ). That said, there is a need to switch to feeding more readily available sources of forage or supplement with other types of feeds during the warm season. You have to be careful with that.

Oats and other grains like corn and barley have become synonymous with vigor in horses, and with good reason. These feeds provide plenty of carbohydrates, fiber, and protein which not only convert into energy in the horse’s body but increase caloric intake.

According to Dr. Williams – Basics of Equine Nutrition, the following are some of the other types of feeds that may be consumed and readily available during the warm season.

OATS – Of all the grains, oats provide the greatest nutritional boost. They are a good source of fiber and much less likely to develop mold or mycotoxins than other grains. With horse nurtrition oats do not have to be processed at all for horses to get the available nutrition, and because they are not processed, they do not spoil as easily as corn or barley.

CORN – Corn is now the most popular type of grain-fed for horses because it is inexpensive and provides a lot of energy. It is nutritious and very palatable to horses. Because corn does not have a hull, it is lower in fiber than oats, but it is also higher in density and digestible energy than oats. Overfeeding corn can cause laminitis, colic, and diarrhea.

BARLEY – Barley has the same protein content as grass hay and should be fed only in rolled or crushed form. The most widely cultivated of all cereal grains in the world, it looks like oats but is very hard and therefore more difficult for horses to chew. Barley has more fiber than corn and more energy density than oats.
However, a word of caution! These cereal grains are not appropriate for many horses. Especially those who are doing little work, and so utilizing high-fat commercial feeds is a safe recommendation!

SOYBEAN – Soybean meal is the most common protein supplement, which averages around 44% crude protein. The protein in soybean meal is usually a high-quality protein with the proper ratio of dietary essential amino acids. Cottonseed meal (48% crude protein) and peanut meal (53% crude protein) are not as common for horses as soybean meal.

VEGETABLE OIL – Vegetable oil is the most used fat source in horse feeds. If adding the oil supplement as a top dress to feed start with 1/4 cup/feeding and increase to no more than 2 cups/day over the course of 2 weeks for the average size horse (1000 lbs.).

RICE BRAN – Rice bran is a newer fat supplement on the market. It is distributed by some commercial feed dealers. It consists of about 20% crude fat, giving it an energy content of 2.9 Mcal/kg.

With all that we have read so far, we can see it takes dedicated care for our equine companions to be comfortable and healthy during the warm season. Adaptations and adjustments, such as supplements and switching to feeding more readily available sources of forage, can be made to assure they are provided the highest plane of nutrition. As we consider and research how we, the caretakers and owners can maintain our horse’s health and comfortability during this kind of season, it is still important that we take into consideration our horse’s preference and horse nutrition.  When we decide to switch things up and make changes, a visit to the veterinarian is a priority to assure your horses’ nutritional needs are being met.

Dr. Clair Thunes is a horse nutrition specialist and she is also one of our consultants. She has worked with a wide range of horses from lactating mares to competitive driving horses. She specializes in a variety of physiological problems and helps us to provide the best advice to the horses’ owners.


At Cave Creek Equine Sports Medicine & Surgery, we offer our equine veterinary services to horse owners in Scottsdale, Cave Creek, Carefree, Desert Hills, New River, the greater Phoenix area, and all the Westside area (including Wickenburg, Wittman, etc). Get to know more about Cave Creek Equine and our services.

Horse Nutrition References:

  • Is There a ‘Right Kind of Salt’ for Horses? – The Horse
  • Behind the Label of Quality Horse Supplements (
  • How to Choose Quality Nutritional Supplements for Your Horse – The Horse
  • Hot Weather Horse: Summer Tips for Proper Horse Care | NASC LIVE
  • National Animal Supplement Council | NASC
  • Combat Summer Heat and Preserve Nutritional Quality of Total Mixed Rations (TMR) (
  • Choosing Forages for Horse Pastures – The Horse
  • Electrolytes – Kentucky Equine Research (
  • Drinking Behavior of Horses: Six Facts About Water Intake – Kentucky Equine Research (
  • The Basics of Equine Nutrition (
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