Carbs, fats or protein: What’s most important for your horse’s diet?

Grazing Horses


We all admire the equine athlete, the captivating blend of speed, control, grace and endurance. But the added stress of performance requires an optimal diet, with plenty of energy from carbohydrates and fats, high quality protein, adequate minerals, and vitamins.

Carbohydrates, the cornerstone

Carbohydrates supply the foundation for energy needs and fuel quick power bursts. The most significant source of carbohydrates should be forage, fed free-choice to provide an amount equal to 2.5 to 3.5% of his body weight. This is central to your horses’ health. When forage is consistently available (beyond what you believe they’ll initially eat), horses will ultimately self-regulate their intake and eat only what their bodies need. Since the horse’s stomach continually produces acid, an empty stomach will lead to discomfort, ulcers, and irregular hormonal changes.

Besides forage, feed concentrated meals, usually a commercial “performance” mix, or better yet, clean oats with added supplementation. But don’t overdo it. The stomach has a relatively small capacity; a too-generous meal can lead to colic. Too much starch at one time also increases stomach acid, potentially leading to ulcers or exacerbating an existing ulceration. Large, starchy meals may trigger laminitis, and in young horses, high-starch diets can lead to osteopathic disorders. And there are other things to be aware of: If starch is fed in excess without enough forage, the calcium-phosphorus imbalance can lead to tying up, irregular heartbeat, inability to regulate body temperature, impaired joint and bone development, or porous bones than can easily fracture. Limit the cereal grain content of your horse’s diet to 2 lbs at a time (less for growing horses) and combine it with other feedstuffs (i.e. hay pellets, beet pulp, and fatty feeds) to create a meal of no more than 4 lbs (dry weight). Remember proportion: Rely on forage for the majority of the horse’s feed.

Fats for staying power

Fat promotes endurance as another energy source, thereby sparing carbohydrates from being used up too quickly. Fat also prevents lactic acid buildup (lactic acid slows muscle recovery). And fat steadies the blood sugar and insulin response, which smoothes temperament.

But not all fats are the same:

  • Sources such as flax, chia, and fish oils are high in omega-3 fatty acids – these reduce pain and inflammation. They also protect the heart, lungs, joints, feet, and immune function, as well as regulate blood insulin levels. Ground flaxseeds and chia are powerhouses of omega 3s for all horses, especially athletes. When feeding ground flaxseeds, choose a commercial product that has added calcium (to correct for the high phosphorus levels naturally found in flax). Chia is also high in phosphorus, so adding a high calcium feed, such as alfalfa, will balance out the calcium to phosphorus ratio.
  • Avoid overuse of “vegetable oils” (especially corn and soybean oils) – they are high in omega-6 fatty acids, which actually increase inflammation, and hence, pain.
  • Rice bran is an excellent fat source; here again, choose a product with added calcium to balance its high phosphorus content. Rice bran oil contains gamma oryzanol, a natural steroid that promotes muscle development.

When switching to fat as an energy source, it’s best to “train” your horse’s body to choose fat for energy. To do this, increase the exercise intensity, giving your horse at least a month of hard training with extra fat in his diet.

Protein, the body-builder

Protein builds healthy muscle, bone, tendons, and blood, as well as hundreds of other body proteins involved in keeping systems in top working order. A grass-alfalfa hay mixture (no more than 50% alfalfa) will offer a high quality forage-based protein. Commercial feeds should supply between 14 and 16 percent crude protein; most producers boost overall protein quality by adding individual amino acids such as lysine, methionine, and tyrosine, as well as alfalfa and soybean meal. Other sources of protein can be included in the diet, such as copra meal, isolated whey protein, and split peas.

Necessary vitamins and minerals

Grazing on healthy pasture is the best source of vitamins and minerals, but for many horses, hay is the likely forage source. Once fresh grass is cut, dried, and stored as hay, its nutritive value diminishes. For the performance horse, pay close attention to the following:

  • B vitamins for the nervous and digestive systems, and to derive energy from feed. Give a B-complex supplement without added iron, unnecessary to supplement in horses.
  • Vitamin A: Beta carotene, a precursor to vitamin A, is lost in hay. 1-2 lbs of carrots, spread out over the day, will satisfy the horse’s need—and his sweet tooth.
  • Vitamin D protects his bones and joints, and maintains muscle function. D is produced from sunlight, but horses without much sun exposure (or that are bathed or sprayed frequently) need to have added Vitamin D. A safe range is 2-4 IU per lb of body weight.
  • Vitamin C neutralizes damaging free radicals caused by intense exercise stress; promotes respiratory function; reduces inflammation; and prevents lung hemorrhages. C is necessary for collagen production, giving bones and joints their strength. The performance horse should have 3,000 to 10,000 mg of C daily.
  • Vitamin E and selenium: Depending on the work load, supplement 1-5 IU of vitamin E per lb of body weight, and up to 5 mg total selenium per day. Selenium is toxic in relatively small amounts so take time to calculate the total in the whole diet.
  • Minerals: Copper and zinc work together to produce healthy bones, cartilage, and connective tissue, improve stress tolerance and endurance. Too much zinc depresses copper absorption; a ratio of 3:1 zinc to copper is best. A 2:1 ratio of calcium to phosphorus is ideal, though horses can tolerate a ratio of up to 6:1. Magnesium is important for muscle function and a calm disposition; ideally, the amount of calcium should not be more than twice that of magnesium.

Most prepared mineral supplements contain adequate minerals. Test your hay to determine its mineral content and balance them accordingly with the rest of the diet.

Salt, electrolytes and water

  • Your horse needs salt: 1 to 2.5 ounces daily (2 to 5 tablespoons), depending on the amount of perspiration. A plain, white salt block should always be available, but some horses do not lick them adequately. Table salt can be offered free choice and/or added to meals. Use non-iodized salt if your horse already is getting iodine in his feed.
  • Hay is the best chloride source (needed with salt) so offer plenty before exercise.
  • Electrolyte preparations should be added when your horse is exercised and/or heavily sweating, but they do not satisfy the entire requirement – the horse must be in proper sodium balance before using electrolytes. Electrolytes are added to simply replace what is lost from perspiration.
  • Adequate salt encourages water consumption; even slight dehydration can negatively impact performance. Always offer clean, fresh water; salt and/or electrolytes should never be added to the main water supply.

Optimal performance requires optimal nutrition. Provide a high-quality, healthful diet of forage, protein, omega-3 fatty acids, antioxidants and minerals to help your equine athlete meet his toughest performance challenges. There is more on feeding the equine athlete in the Library at


  1. I followed Dr. Getty’s advice, and she is absolutely correct. Our horses self-regulated within a week, and actually decreased their hay intake while on free choice.


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