How Exercise Affects Nutrient Requirements of Performance Horses

Life Stage : Mature - Performance

Kelly Vineyard, M.S., Ph.D.

Senior Nutritionist, Equine Technical Solutions

When feeding performance horses, it is important to provide fuel for energy expenditure, replenish nutrients for muscle function and repair, and support optimal health through a balanced diet.

Specific nutrient requirements that are affected by exercise include:
  1. Energy
  2. Water
  3. Electrolytes
  4. Protein and amino acids
  5.  Vitamins and minerals


The primary energy sources in a horse’s diet are carbohydrates and fat. There are two general categories of dietary carbohydrates: non-structural and structural.
Non-structural carbohydrates (NSC) include sugars and starches digested in the small intestine. Structural carbohydrates include fibers digested in the hindgut (cecum and large colon). The end-product of NSC digestion—blood glucose—serves as a readily available source of muscle fuel, or it can be stored as fat or glycogen. This makes sugar and starch useful components in the performance horse diet. The end-products of fiber digestion—volatile fatty acids—are primarily used for maintenance energy requirements but can also be used less efficiently as fuel for exercise.
infographic of 4 nutritional needs for performance horsesFat, the other primary energy source, contains 2.25 times more energy than an equal amount of carbohydrate and is the most abundant source of stored energy in the horse’s body. It also provides essential fatty acids, which are important components of cell membranes and are vital for skin, coat and hoof health, and to certain aspects of immune function. Good sources of fat include vegetable and marine oils, flaxseed and rice bran. 


Water is one of the most overlooked nutrients affected by exercise. A horse can ingest water by drinking or eating moist feed, which can contain anywhere from 10 to 80 percent water. Horse hay and grain contain around 10 percent water, whereas fresh grass is approximately 80 percent. A horse loses water through urine, feces, sweat and the respiratory tract. Lactating mares also lose water through milk.
Loss of water through sweat is greatly affected by the environment. For every hour of exercise, a horse will lose 1 to 2 gallons of sweat when temperatures are below 68°F, and up to 3 to 4 gallons when temperatures are above 86°F. To maintain proper hydration, an exercising horse should consume 10 to 20 gallons or more of water per day. Keep water buckets and troughs clean while providing adequate electrolytes through the diet to promote water intake and help prevent dehydration.


A horse’s body cannot store electrolytes; they must be provided through the diet to replenish what is lost in sweat each day. Horse sweat contains a high concentration of sodium, chloride, as well as potassium, calcium and magnesium. Maintaining the correct electrolyte balance is essential to support the horse’s thirst reflex and proper muscle function.
Generally, proper electrolyte levels can be supplied by the horse’s diet if the daily ration consists of moderate-quality forage, a fortified commercial grain mix and if supplemented with 1 to 2 ounces of salt or commercial electrolyte preparation.
Supplemental salt should be plain white salt (iodized or non-iodized is acceptable) provided in block or loose form for free-choice consumption. Offering a salt block for horses may not deliver enough for the diet because horses are not natural lickers. Instead, loose salt for free-choice consumption or as a top-dress may be preferable.
Avoid over-supplementation of electrolytes in diets for performance horses. For example, forages generally contain 1 to 2 percent potassium, meaning typical horse diets have too much and supplemental potassium may not be required. Administering additional electrolytes to an already-dehydrated horse can cause significant problems, and repeated oral administration of electrolyte solutions has been shown to exacerbate gastric ulcers.

Protein and amino acids

Not all protein is created equal, and horses have an amino acid requirement rather than a protein requirement. Feeding a commercially prepared concentrate containing high-quality protein sources, like soybean and alfalfa meal, along with additional individual amino acids, will promote muscle tone and a strong topline.
Horses in low-to-moderate work often do not receive adequate protein in their diet. These horses do not require additional calories and are fed primarily grass hay and little to no concentrate. They have plenty of rib cover and are potentially overweight at a 6.5 to 7 body score, but have a poorly developed topline, especially over the loin, due to protein deficiency. These horses would benefit from a ration-balancing feed, such as Purina® Enrich Plus®, to supply the necessary protein, vitamins and minerals needed for work without unnecessary calories.
Feeding excess protein to performance horses is also common, especially for horses with high energy demands. Excess occurs when feeding high-quality, alfalfa-based hays in large quantities, or by adding protein supplements to a diet that already has enough. Horses are tolerant of a moderate excess of protein because it can readily be eliminated through the urine. However, once the total protein level of the diet approaches 25 percent, athletic performance can suffer from the resulting increased sweat loss, heart rate and respiratory rate caused by excess dietary protein. The total protein concentration of a performance horse diet (forage plus concentrate) should be between 10 to 16 percent to prevent the negative effects of protein excess.
Certain amino acids, such as lysine, threonine and methionine, are significant components of muscle protein and are essential for muscle growth, development and repair. They are considered essential, as horses cannot make them, and they must be supplied through the diet.
Purina® SuperSport® amino acid supplement offers a blend of amino acids, vitamins and minerals proven to support muscle performance in exercising horses. Horses fed Purina® SuperSport® have shown improvements in muscle development, exercise recovery and overall athletic fitness and performance when compared to horses not receiving the supplement.

Vitamins and minerals

The increased vitamin and mineral needs of the exercising horse can generally be met with a well-fortified diet. Feeding a concentrate from a reputable feed manufacturer formulated specifically for the performance horse will ensure these needs are met. Because of the complex nature of balancing a diet for proper nutrient levels and ratios, it becomes more challenging when attempting to meet a horse’s vitamin and mineral needs through straight grains and/or individual supplements.
Vitamin E is important for performance horses because of its role in combating muscle damage caused by free radicals produced during exercise. The moderately exercising horse should receive at least 1000 IU of vitamin E per day. There is some evidence that vitamin E supplied at levels up to 3,000 IU per day may provide additional benefit, especially for horses suffering from neurological or muscle abnormalities.

Bottom line

By taking time to understand how exercise affects the nutrient requirements of your horse, you can more effectively choose a nutrition program that will complement your training program. Seeking advice from professionals is also a good option when you have a specific question.
Looking for the right feed to meet nutritional requirements for your performance horses? Use the Feed Finder to try a Purina® horse feed.