United States Eventing Association

When feeding a performance horse, it is tempting to begin with what goes into the feed bucket. Which feed supplies the best fuel? What supplements are needed to maximize performance?

Those are reasonable questions, but they are not a good starting point.

Those are reasonable questions, but they are not a good starting point.

Before deciding on anything that comes in a scoop, horse owners should start by evaluating what makes up the largest proportion of the diet. Forage is not simply something that keeps a horse occupied between meals. It is the primary feed source a horse’s digestive tract was designed to process, a major contributor of energy and nutrition, and the foundation upon which the rest of the ration should be built.

For the event horse, that foundation must support the strength and precision required for dressage, the stamina needed for cross-country, and the power and speed required for show jumping. A forage-foundation approach helps meet those varied demands effectively, while supporting digestive health, natural feeding behavior, and overall wellbeing.

How the Equine Digestive System Works

Horses evolved as grazing herbivores, consuming fibrous plants in small amounts over many hours each day. Their digestive anatomy still reflects this.

The horse has a relatively small stomach that continuously secretes acid, whether feed is present or not. Frequent forage intake encourages chewing and saliva production, helps buffer stomach contents, and creates a mat of fibrous material that can reduce acid exposure in the upper portion of the stomach.

Most dietary protein, fat, soluble carbohydrates, vitamins, and minerals are digested and absorbed in the stomach and small intestine, though some minerals, notably phosphorus, are absorbed further down the tract. Fiber, however, passes into the cecum and large colon, which together form a large fermentation chamber populated by bacteria, protozoa, fungi, and other microorganisms, collectively referred to as the intestinal microbiome.

This is what classifies the horse as a hindgut fermenter. Horses do not produce the enzymes necessary for fiber digestion, and it is up to these microbes to extract energy and nutrition from plant fiber through the process of fermentation.

This system works remarkably well, provided the horse receives enough forage and if dietary changes are made gradually. It is less forgiving when large concentrate meals are fed, abrupt feed changes are made, or when the forage is of poor quality, reducing the ability of the microbes to do their job well.

Fiber Fermentation and Energy Production

The structural carbohydrates in forage, primarily cellulose, hemicellulose, and pectin, cannot be digested by the horse's own enzymes. Hindgut microbes ferment these fibers and produce volatile fatty acids (VFAs). Acetate is by far the most abundant, followed by propionate and butyrate. The horse absorbs these VFAs and uses them as fuel. Acetate can be used by muscle and other tissues or stored as fat. Propionate can contribute to glucose production in the liver. Butyrate is an important energy source for the cells lining the large intestine, and it helps keep the gut wall healthy.

Forage can supply far more usable energy than it is usually given credit for. Depending on maturity, digestibility, and intake, good-quality forage may be able to supply 100% of a horse’s energy needs at maintenance or in lighter work, and it can provide a substantial share of the calories needed at higher workloads.

A hindgut that is holding fiber also serves as an important reservoir of water and electrolytes, making it an often-overlooked part of a good hydration strategy. Yes, that fiber adds weight. But it is working weight, not dead weight, and viewing it as simply “gut fill” sells it short. Forage is a fuel source, a nutrient source, and part of a built-in water supply system the horse can draw upon.

What Happens When Forage Falls Short

Forage can fall short in several ways. The horse may simply not receive enough, the hay may be too mature and poorly digestible, or pasture may supply less usable dry matter than it appears. Waste, poor appetite, dental issues, travel, and restricted access can further reduce intake.

The most obvious result of inadequate forage is decreased calorie intake. The horse may lose weight, struggle to maintain topline, or recover poorly from training. Adding more concentrate without identifying the forage deficit can make the ration increasingly dependent on large meals of energy-dense feed.

That can create a second problem. When starch intake exceeds what can be efficiently digested in the small intestine, that starch will spill over into the hindgut. Rapid fermentation of that starch produces lactic acid, which lowers hindgut pH and can disrupt the microbial population, leading to digestive upset. Low forage intake and long gaps between meals are also associated with gastric ulcer risk and undesirable behaviors such as wood chewing and bedding consumption. These are all reasons to prioritize forage quality and continuous access.

In other cases, forage supplies enough calories but falls short in protein quality and/or essential vitamins and minerals. Mature grass hay may maintain body weight yet fail to provide enough lysine for a horse rebuilding topline. Regional forage may consistently undersupply copper, zinc, selenium, or other nutrients. A good quality grass hay may be nutritionally dense and high in sugar and starch, making it inappropriate for insulin-dysregulated horses.

This is why "forage-based" should not be confused with "forage-only." Forage establishes the baseline. The rest of the ration should complement the forage by correcting its limitations, not compete with it.

Knowing What Makes Good Forage

Good forage is forage that is clean, palatable, digestible, and most importantly, appropriate for the individual horse it is being fed to. It is not defined by one species, one cutting, or one number on a forage analysis.

Start with cleanliness. Hay should be free of visible mold, excessive dust, foreign material, and off odors, and it should be stored dry. Pastures should be evaluated for toxic plants and overgrazing.

Next, consider maturity and physical characteristics. Leafier, less mature forage is generally more digestible and calorie-dense than coarse, stemmy forage harvested later. However, the richest hay is not automatically the best choice. An easy keeper may benefit from a more mature, lower-calorie forage, while a hard-working event horse with a limited appetite may need a more digestible and palatable option.

Visual inspection cannot reveal the full nutrient profile. A laboratory analysis provides measures such as dry matter, crude protein, neutral detergent fiber, acid detergent fiber, calcium, and phosphorus. Sugar and starch are important values to assess for horses with insulin dysregulation, laminitis risk, or certain muscle disorders. A broader mineral analysis may be warranted when forage makes up most of the diet.

Building the Ration Around Forage

Begin by estimating the horse's body weight and measuring actual forage intake. For most adult horses, forage intake commonly falls near 1.5 to 2 percent of body weight per day on a dry matter basis, with many horses consuming more when forage is freely available. The appropriate amount depends on body condition, workload, metabolic status, forage energy density, and total ration composition.

For a 1,200-pound event horse, the difference between 18 pounds (1.5% BW) and 24 pounds (2% BW) of forage per day, measured on a dry matter basis (roughly 20 and 27 pounds of typical hay as fed), is meaningful. So is the difference between a highly digestible early-cut hay and a mature, stemmy hay. It’s critical to measure hay by weight, as opposed to by the flake, to accurately assess daily intake. To get a fairly accurate estimate of flake weight, take the average weight of multiple flakes for each of the hay types being fed.

Once forage intake and nutrient content are known, compare them with the horse's requirements and aim to fill the gaps.

For an easier keeper, forage may meet calorie needs but will likely still lack vitamins, minerals, and amino acids. These horses may need only a ration balancer or concentrated vitamin-mineral supplement. A horse in heavier work may require additional calories from a fortified performance feed that includes added fat and digestible fiber. A horse with limited chewing ability may need chopped, pelleted, cubed, or complete forage replacements.

Meal size and timing also matter. Divide concentrates into multiple meals, avoid abrupt changes, and aim to provide consistent forage access during travel and competition. When practical, do not ask a horse to train, ship, or stand for long periods on an empty stomach. Bring familiar forage from home or transition well in advance to what will be available at the venue. Incorporating bagged forages, such as those manufactured by Standlee Premium Products, into a horse’s daily ration is another way to provide some consistency when local forage sources are frequently changing or when travelling.

The Solid Foundation

Performance nutrition can become complicated quickly. There are many effective ways to increase calories, support muscle recovery, replace electrolytes, and meet micronutrient requirements. None of them eliminate the need to understand and prioritize the forage component of a horse’s diet.

Before adding another concentrate or supplement, ask these five questions:

1. How much forage is the horse actually eating?
2. Is it clean, palatable, and appropriate for the individual horse?
3. Does this forage match my horse’s needs, or should I change to a different type or a better-quality forage?
4. Where are the true nutritional gaps?
5. What is the specific purpose of anything being added?

Answer those questions first, and the rest of the ration becomes easier to build. More importantly, it becomes a ration designed with both the physiological and psychological needs of the horse in mind.

Written by Kelly Vineyard, MS, PhD
EquiVine PhD Nutrition
Standlee Equine Nutritionist