Equine nutritionist, Dr. Shannon Pratt-Phillips, answers some of the most common questions owners have about feeding their horses and their nutrition.

1. What nutrients do horses require?

Aside from water, which is the most important nutrient, horses need a balanced diet including energy (calories), protein, minerals and vitamins.

Horses get energy/calories via the metabolism of fats, carbohydrates and proteins. Per unit weight, fats provide more than two times the calories of carbohydrates, which are often further classified as complex carbohydrates (fibres) and simple carbohydrates (starches and sugar). Because fibre isn’t as well-digested as starch and sugar, feeds higher in starch and sugar (such as cereal grains or grain mixes) provide more energy/calories per unit weight than high fibre feeds such as hay (though both substantially less than fat). Protein metabolism for energy is not terribly efficient, so protein is not actually an ideal source of calories for horses. However, they do need protein for providing the building blocks for making structural tissue (like skin or muscle), enzymes and hormones.

Minerals include the macro minerals (calcium, phosphorus, sodium, chloride, potassium, magnesium and sulfur) and microminerals (including zinc, copper and selenium among others). These are often found in good quantities in forages or pasture, but horses likely need supplementation with salt and perhaps selenium, as well as some other trace minerals if they are not in their hay.

The key vitamins horses need in their diets include vitamin A (beta carotene), vitamin E and vitamin D (which can also be synthesized by the skin with exposure to sunlight). These are all found in good amounts in pasture, but tend to decrease over time with storage. The B complex of vitamins and vitamin K can be synthesized by the microbial organisms in the horse’s digestive tract, and are also found in most equine feeds, so they rarely need supplementation. Vitamin C is synthesized by the horse (unlike humans, guinea pigs and fruit bats) so is, therefore, not considered an essential nutrient, though older horses may require some supplementation.

2. How much hay should my horse get each day?

A general rule of thumb is that a mature horse should consume at least one per cent of his body weight as hay or other forage per day. So, an average 500kg horse, should receive at least 5kg of hay daily. (Note that hay has about 10 per cent water, so if your horse consumes only pasture, which is closer to 50 per cent water, you must adjust the amounts accordingly.)

If offered free choice, most horses will consume about two per cent of their body weight each day, though some may consume more. Some horses (ponies, in particular) have been shown to consume up to five per cent of their body weight of (dry) pasture!

Hay satisfies three important things for the horse:

1. Nutrition: Good quality hay (or pasture) can provide all of the energy (calories) and protein a horse needs, as well as much of the minerals and vitamins (particularly pasture) that most horses need (particularly maintenance horses, or those in light work or even early gestation);

2. Fibre for gut health: While there isn’t a set amount of fibre a horse needs, fibre that is found in hay, pasture and feeds like beet pulp and rice bran is required to keep the microbial organisms of the large intestine happy, and to help ward off gastric ulcers;

3. Natural behavioural imperatives: Horses evolved to eat 18+ hours per day, and those that don’t get enough forage to satisfy their natural grazing behaviour are prone to developing stereotypic behaviours such as cribbing or stall-walking.

Depending on the weight of your hay flakes, which vary tremendously between different types of hay or even within the same bale, at minimum a horse would need about three to five flakes per day (one per cent body weight), but would more likely eat between six to ten flakes per day.

3. Do I need to get my horse’s hay analyzed?

Yes! A simple hay analysis (to get values of energy/calories/nutrition, protein, major minerals like calcium, phosphorus and magnesium, etc.) can be very useful in determining which nutrients your horse can obtain from his hay, so that you will know which nutrients – if any – are still required and need to be provided for elsewhere (such as via grain or supplement). Many agriculture labs will analyze a sample of hay for as little as $20.

4. What is the difference between a grass hay, legume hay or haylage?

Hay is simply cut and dried stalks of plants, with grass hay coming from grass plants and legume hay coming from legume plants. Examples of grass species include timothy, orchardgrass, bluegrass, fescue and brome. Examples of legume species include alfalfa and clover.

Haylage is made from grasses or legumes that have been cut, but not allowed to dry completely and are baled within a plastic wrap. This keeps the moisture in, and allows the plants to ferment, which often improves the digestibility of the plants. There is a small risk, however, that haylage can spoil and cause botulism, so it is usually recommended that those who feed haylage frequently vaccinate their horses against botulism.

Hay or haylage made from legumes tend to have more protein and calcium (and a slightly higher energy/calorie density) than hay or haylage made from grasses.

5. Does my horse need grain?

It depends. “Grain” (cereal grains, commercial mixes or pellets) is generally added to a horse’s diet to increase the calorie (energy) density of the diet, but commercially manufactured feeds often also contain added protein, vitamins and minerals, as recommended for different classes of horses (such as growing horses or performance athletes). So, if your horse has nutrient requirements above what hay or pasture can provide (because their requirements are too high, they can’t eat enough of the hay, if the hay is poor quality, or if hay/pasture is scarce in times of a drought) then grain mixes may be useful to supplement your horse’s diet.

Because we are seeing numerous overweight and obese horses, it is important to determine if your horse truly needs extra calories, or if they just need the protein/vitamins/minerals. If it is the latter, a more concentrated feed mix (called a ‘balancer’) may be useful, where horses are fed in amounts of about 1kg/day. If your horse is actually overweight, it may make more sense to simply offer a pelleted vitamin/mineral supplement, that is fed in amounts of 100g or less per day, which would only supply a negligible amount of calories for a horse that not need them!

6. Why is everyone talking about ‘NSC’ – what is that?

NSC stands for “non-structural carbohydrate,” and is the fraction of the feed that is made up from starches and sugars. This information about a feed can be useful for owners of horses that are sensitive to large amounts of NSC in their diet, such as horses with behavioural issues (see #9) or metabolic problems (such as insulin resistance, Equine Metabolic Syndrome or Polysaccharide Storage Myopathy).

Many feeds (particularly some grasses and cereal grains such as corn) are high in starches and sugars that can potentially be dangerous to some horses, and, as such, owners should aim to keep NSC intake low. Owners should also remember to not only focus on the NSC content of their grain mix, but also their hay – because hay is fed in greater quantities. A ‘low’ NSC hay, at 10 per cent NSC fed at 10 kg per day, for example, would provide 1,000 grams (1kg) of NSC. While feeding only 1kg of a ‘high’ NSC grain, at 40 per cent NSC, provides 400 grams of NSC. Note that it wouldn’t be recommended to decrease the hay, because that is so important for the horse’s health (see #2). Instead, look to minimize overall intake of NSC through finding the lowest NSC hay and grain mix.

7. Does my horse need supplements?

It depends on your horse’s needs and what else is being fed. If your horse has free access to fresh, clean water and good quality pasture, and has relatively low nutritional needs (maintenance, light work, etc.), the only thing that won’t be in the water and pasture would be some minerals – like salt and maybe selenium. In this case, a trace mineral salt block is sufficient.

In winter, or when pasture isn’t available, and where good quality hay is the primary feed, your horse may also need added vitamins because these breakdown in stored hay over time. A general vitamin/mineral supplement is usually good here (and if you have a hay analysis, you can figure out if your horse needs added protein too, though decent quality hay is usually a good source of protein).

If your horse is being offered a commercially formulated mix at amounts recommended by the manufacturer, the feed will contain all of the vitamins and minerals needed for that horse, and no additional supplementation is required. If you feed less than the suggested amounts, or if you feed cereal grains (like oats, etc.), however, you will also need to supplement with some vitamins and minerals.

While salt (sodium chloride) is added to commercial feeds, offering a plain white salt block is fine to allow a horse to get additional salt if they need it, and if your horse is in work, additional salt and other electrolytes may be required.

Other nutritional (extra vitamin E or biotin) and non-nutritional supplements (such as herbs or joint supplements) may be recommended for your horse upon consulting with a nutritionist or veterinarian.

8. Why do some people offer feeds like hay cubes, wheat bran, beet pulp, rice bran or oil?

There are many reasons why an owner would feed their horse ‘other’ types of feeds.

Hay cubes are often fed to horses that may have poor teeth and require soaked and easily chewed hay, or horses that have breathing issues and don’t do well with long-stem (and potentially dusty) hay.

Wheat bran is often fed as a ‘mash’ along with water and other ingredients to help serve as a laxative, though that is unfounded. Beet pulp and rice bran are high fibre feeds, so they are beneficial to the horse’s digestive tract, but tend to provide more calories per unit weight than hay or other forages. They are, therefore, often offered to increase the calorie intake for a horse, while not increasing the sugar/starch intake that usually comes with feeding cereal grains for energy, because they are low in NSC.

Hay cubes, wheat bran, beet pulp and rice bran are usually fed soaked, and may also be useful for horses that don’t consume any ‘grain’ to mix in vitamins and mineral supplements, while not providing too many calories (if offered in moderation).

Oil is often fed for horses that have high calorie requirements (such as horses at work or hard keepers) to increase the energy (calorie) density of the diet, without having to increase the grain (and therefore again not increasing the starch/sugar in the horse’s diet). Some oils (such as the omega-3 fatty acids found in fish oils, and to some degree in flax oil) can also provide anti-inflammatory and/or immune benefits to some horses.

9. What can I feed to boost my horse’s energy, or to calm him down?

Recall that energy = calories, so when someone asks about boosting energy, they usually are asking how to increase the horse’s gusto and oomph. The two biggest things that will affect a horse’s attitude towards exercise are breed/temperament and athletic fitness.

Many times, when an owners asks about ‘increasing energy’ their horse is actually fat and, therefore, has lots of energy (calories), but it’s stored as fat. If a horse were to lose that weight, he would not have to work as hard, and would be more willing to work.

Fitness level will also increase their motivation to work. Similar to humans, you can’t feed someone a bunch of donuts and chocolate bars and hope they run faster on the treadmill!

On the flip side, some horses are ‘hot’ and have too much oomph, as a result of being very sensitive to sugar in their diet (similar to a kid after eating a chocolate bar). These horses tend to do better if sugar (starch/sugar) is restricted in their diet.

10. How can I tell if my horse is deficient in a nutrient?

It is usually pretty easy to tell if your horse is deficient in water (he becomes dehydrated) or energy (he loses weight), but others can be more difficult to determine.

Protein deficiency usually results in poor coat and hoof quality, as those tissues have rapid turnover. With minerals and vitamins, it can be harder still, because signs of deficiency may be a result of several different nutrients, and it may be difficult to tell which one is the cause.

Unfortunately, blood samples are often a poor indicator of nutrient deficiency. If a horse is fed a calcium-deficient diet, for example, their blood calcium is usually normal, because calcium is removed from the bone in an effort to keep blood calcium stable. The best way to determine if your horse is meeting his nutrient requirements is to fully analyze his diet – including hay analysis and grain analysis, ideally with a full vitamin and mineral analysis.

Other than looking at the diet, the best way to determine if calcium status is good is to take an x-ray to determine the bone calcium density. Urine analysis is also usually a poor indicator, and tissue analysis (such as a liver biopsy to determine vitamin A status) can be invasive. Hair analysis gives no indication about nutritional health, other than for some trace minerals, such as arsenic (!).

If you are concerned about your horse’s nutrient status, you are best to visit with an equine nutritionist who can perform a thorough dietary evaluation, and could recommend further testing if needed.


Many feed stores and companies have representatives that have been trained in equine nutrition (either formally through a university degree or through their own company training) and can be a very good source of information. As you can imagine though, there may be some bias to the feeds (and amounts) they recommend.

Independent equine nutritionists who offer nutrition consulting generally have advanced (Master of Science and/or Doctoral/Ph.D.) degrees in equine nutrition and will offer unbiased evaluations of your feeding program, and can make recommendations or assist you with formulating your own ration. Veterinarians and farriers may also offer nutritional advice, but usually do not have the specific education and training in equine nutrition to help you formulate a diet for your horse.

Whoever you find to help you, be sure to ask about their nutrition education (again, some may have an undergraduate course in equine nutrition, some may have a non-university course in equine nutrition, while others will have taken graduate courses in equine nutrition and conducted feeding trials are part of their research) and experience. You may also consider what professional organizations someone belongs to (such American Registry of Professional Animal Scientists, Equine Science Society or American Academy of Animal Nutrition). As with most things, you get what you pay for, and more education and experience usually costs (and is often worth) a little more.