If not well managed, pasture often does not meet a horses forage requirements. | Photos.comForage is the most important part of a horses diet and is the foundation to build the rest of the diet on, said Clair Thunes, MS, PhD, PAS, equine nutrition consultant and owner of Clarity Equine Nutrition, during her presentation at the 2026 EquiSUMMIT Equine Nutrition & Health Conference, hosted by Kemin Industries.Horses evolved eating grass with low nutritional value, so they had to eat large quantities, grazing for 16 to 18 hours a day. When humans domesticated horses, they restricted grazing time and began feeding them starch-rich meals to maintain condition for their work levelWe moved them away from a forage first diet despite the fact that the horses digestive tract did not change and is still a forage vat designed to ferment fiber, said Thunes. What is Forage for Horses?Forage is primarily composed of carbohydrates, specifically structural carbohydrates such as cellulose and hemicellulose found in the plant cell walls, which provide rigidity to the plant. Forage can also serve as a good source of protein as well as some vitamins and minerals.While horses themselves do not have the enzymes to break down cellulose, the microbes in the gastrointestinal tract that make up the intestinal microbiome do have those enzymes and can break down the structural carbohydrates, said Thunes.Horse Forage Testing and CompositionTo determine the content of your hay, Thunes recommended collecting a sample and sending it for analysis. Take a core sample of about 15 to 20 different bales and use a proper hay probe to take those samples, she said. Use a laboratory that specifically tests hay for horses.This forage analysis will tell you the amount of structural carbohydrates as well as the nonstructural carbohydrates (NSC, i.e., starch and sugars), which are found inside the cells and available for absorption in the horses small intestine. The report will also show the mineral and crude protein content of the hay.The acid and neutral detergent fiber (ADF and NDF, respectively) are both carbohydrate fractions. The ADF represents the cell wall fraction. The higher the ADF, the less digestible the forage is.Forty percent or higher is quite indigestible, whereas low 30s has a higher digestibility, said Thunes. So, for a metabolic horse, owners will likely be looking for a forage lower in digestibility and therefore with a higher ADF. This means you can feed more hay and not get as much nutrition out of it. We can therefore honor digestive tract physiology by providing forage while minimizing the chances of becoming overweight.Hay analysis will also provide information on water and ethanol soluble carbohydrates (WSC and ESC) and NSC. The consensus is that we should be concerned about the NSC content of forages for metabolic horses, which is the WSC plus starch on forage analysis, said Thunes.In general, experts advise offering metabolic horses, those with insulin resistance, and even horses with type 1 polysaccharide storage myopathy (PSSM1) a hay containing less than 10% NSC on a dry matter basis.Pasture Problems: Inadequate ForageMany horses depend on pasture for forage intake, yet pasture management often falls short.Horses can graze extremely close to the ground and can kill off a pasture if it is not well managed, said Thunes. If pasture is grazed until there is no leaf left, the plant has minimal ability for photosynthesis and therefore uses energy from the roots, killing the root system. Over time, the plant will die and pasture quality decreases.This leaves horses with pasture that has no nutritional value. Once the pasture is grazed to 4 inches, the pasture needs to be rested until it reaches 6 to 8 inches again, she said.Picking an Appropriate Forage For Your HorseGrass hay contains fewer calories per pound than alfalfa, which means you can feed more before hitting the horses caloric requirement. Therefore, easy keepers can be fed more grass hay than alfalfa and, as mentioned above, the more forage a horse can consume, the better their gastrointestinal health.Grass hay comes in cold- and warm-season varieties. Cold-season grasses such as fescue store carbohydrates as fructans. Warm-season grasses such as Bermuda grass and teff store carbohydrates as starch, which is limited and is why warm season grasses tend to be lower in NSCs than cold season grasses.Cold-season hays therefore tend to be higher in NSC, but not always, said Thunes. Teff isnt always low in NSC, which is why it is so important to have the hay tested and know the NSC content.Alfalfa, she added, is a very different forage. It is high in protein and therefore often recommended for performance horses, young stock, and broodmares. It has a high calcium-to-phosphorus ratio, so Thunes recommended restricting alfalfa to less than 25% to 30% of the forage intake. Feeding too much alfalfa leads to excess protein consumption that cant be stored in the body. It needs to be broken down and excreted as urea.The high calcium and protein, however, can help buffer stomach acid and help horses that struggle with ulcers, said Thunes. Owners just need to balance the pros and cons of feeding alfalfa.Consult your veterinarian and an equine nutritionist to determine what forage is best for your individual horse. Take-Home MessageForage should make up the bulk of a horses diet (ideally a minimum of 1.5% of the horses body weight per day) and be tested for suitability for the type of horse you have. A hay that might not be a good hay for one horse might be an excellent choice for another horse, said Thunes.