How Much Fiber Does My Horse Need?

Fiber is one of the most important nutrients for any horse. Not only does it provide the horse with most of its energy each and every day, but it also helps keep their digestive system healthy and functioning. However, exactly how much fiber a horse needs each day is still not clear. Still, we can deduce how much fiber a horse may need each day by evaluating their forage requirements.

Why is Fiber so Important to Horses?

We also asked this question in our Good vs. Bad Fiber in Horse Diets article. Yet, it is worth a quick review because it is that important!

Briefly, because horses are hindgut fermenters, they require fiber to help feed the beneficial microbes in their digestive tract. In turn, as these microbes digest the fiber, they produce volatile fatty acids (VFAs) and B-vitamins. The VFAs are absorbed and utilized by the horse as energy. In many instances, this can provide as much as 70% of a horse’s daily energy requirement.

Some of the other benefits of fiber not previously mentioned include:

  • Feedstuffs high in fiber help horses with gut fill and a feeling of satiety (fullness).
  • Higher fiber feedstuffs help slow down digestion. This allows the digestive enzymes and microbes to properly break down feedstuffs.
  • Forage slows down a horse’s feed intake. Thus, it remains in the horse’s stomach longer and this can help with reducing the risk of gastric ulcers.

Can Horses Be Deficient in Fiber?

Horses can become deficient in fiber, leading to many detrimental health issues. This can also be caused by feeding horses low quality fiber. Horse diets deficient in fiber can result in:

Diets usually become deficient in fiber when horses are not fed enough forage. Deficiency can also result from the feeding of low-quality forage. Poor quality forage is usually higher in lignin, a non-digestible fiber, rather than the preferred digestible fibers of cellulose and hemicellulose. With less digestible fiber, the microbe populations in the horse’s hindgut suffer and produce less VFAs, B-vitamins, and result in the abovementioned disorders.

This highlights the importance of feeding high quality fiber and avoiding feeding your horse low-quality fiber sources, including:

  • Straw: very high in lignin and provides little nutritional value to horses.
  • Corn stalks: very high in fiber, but cannot be digested by the horse. Additionally, they can be contaminated with molds or toxins, which can be extremely harmful to a horse.
  • Feed with rice, oat, or peanut hulls as a fiber source: often used to increase fiber levels in a lower quality horse feed and usually higher in indigestible fiber.
  • IHHigh-NSC horse feeds: Feeds that are high in sugars and starches can disrupt the beneficial hindgut microns and lead to digestive disorders, such as colic or laminitis.

How Much Fiber Does My Horse Need Each Day?

Surprisingly, there is no set amount of fiber a horse needs per day. This has never been established by the National Research Council’s (NRC) nutrient guidelines for horses. However, the NRC does recognize fiber as one of the most important nutrients for horses. They also note that multiple studies have shown detrimental effects on horses’ health when they were fed diets low in fiber.

Even though the amount of fiber a horse needs each day has not been established, the amount of forage/hay a horse needs each day has been established. Thus, you may notice fiber and forage are often interchangeable terms when experts discuss fiber in the diet of horses. The NRC states that the absolute minimum any horse diet should be is 1% of bodyweight as forage (dry matter) per day.

The 1% of body weight forage recommendation is listed as “dry matter (DM)” per day and is important to highlight. All feeds will have some moisture content and the amount will vary. For example, fresh green grass has much more moisture than sun-cured grass hay. So, it is important to take account when determining the absolute minimum amount of forage (dry matter) a horse may need each day.

Average dry matter content of some feedstuffs:

  • Alfalfa hay, 90% DM
  • Dehydrated alfalfa cubes, 90% DM
  • Fresh alfalfa, 24% DM
  • Dehydrated beet pulp (shreds), 92% DM
  • Beet pulp wet, 17% DM
  • Bermuda coastal hay, 89% DM
  • Fresh spring grass, 18% DM
  • Late season spring grass, 47% DM
  • Oat straw, 91% DM
  • Rye grass hay, 90% DM
  • Timothy hay, 88% DM

When calculating bare minimums of forage needed for a horse, it needs to be calculated as DM to ensure you are meeting the horse’s daily fiber needs. For example, using 1% for a 1000-pound horse would equate to 10 pounds of DM as the bare minimum. To keep it simple, this would be approximately 11 pounds of a 90% DM forage fed to a 1000-pound horse. Again, this is the bare minimum to keep the horse healthy.

However, here we are talking about bare minimums and not necessarily what is best for the horse. The forage recommendations for horses are now in the 2% to 3% of their bodyweight per day range. after so much nutritional research, we now understand fiber as being that important! Thus, a typical 1000-pound horse should optimally receive 22 to 33 pounds of forage per day.

Take Home Message

How we feed horses has changed drastically in the last two decades. Today, it is recognized that nutrients like fiber are critical to a horse’s health, well-being and performance. While the exact requirements of fiber have yet to be established, we have established minimum forage requirements. These are helpful in guiding us on how much fiber a horse truly needs. As long as a horse is receiving their bare minimum of 1% of their bodyweight per day in the forage DM, you can be assured your horse is receiving their daily requirements of fiber. However, it is highly recommended that every horse should be offered 2% to 3% of their bodyweight per day in forage DM for optimal health and performance.

If you are having trouble evaluating the fiber in your horse’s diet or need general nutritional advice, please feel free to contact us for a free consultation at any time!


National Research Council. (2007). Nutrient requirement of horses, 6th rev. ed. National Academies Press.

UC Cooperative Extension. 2015. Average dry matter percentages for various livestock feeds. Link HERE

Article By: Chris Mortensen, Ph.D.
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