What Nutrients Are in Grass? Macro & Micronutrients

Grass is far more nutrient-dense than its plain appearance suggests, packing a complex mix of carbohydrates, proteins, fats, minerals, vitamins, and defensive compounds into every blade. The exact profile shifts dramatically with grass species, soil conditions, season, and the age of the plant at harvest. For grazing animals, grass can supply most of what they need to survive; for humans interested in wheatgrass or barley grass, the young shoots concentrate vitamins and antioxidants in forms our bodies can actually use. Understanding what is in grass, and why those nutrients fluctuate, matters whether you manage pastures, feed livestock, or just want to know what makes a lawn tick.

Structural Carbohydrates Make Up the Bulk

The single largest component of grass, after water, is structural carbohydrate. Cellulose and hemicellulose form the scaffolding of cell walls, and together with lignin they account for the majority of the dry matter in most grasses. These fiber fractions are measured as neutral detergent fiber (NDF) and acid detergent fiber (ADF). In a tropical signal grass, for example, NDF ranged from about 64% to 65% of dry matter, while ADF sat between roughly 37% and 44%.¹ Native warm-season grasses in mixed stands showed NDF values from around 620 to 710 grams per kilogram of dry matter, depending on how long they grew before being cut.² The practical takeaway: well over half the dry weight of a mature grass plant is cell-wall fiber.

Lignin, the rigid polymer that stiffens plant tissue, deserves separate attention because it is essentially indigestible even for ruminants. In meadow plants, lignin content varied from about 47 to 52 grams per kilogram of dry matter depending on species, and it climbed as plants were left to mature longer before cutting.³ In range grasses studied through a full growing season in Sudan, lignin rose to nearly 35% of dry matter by the 27th week of growth.⁴ More lignin means less digestible energy for any animal trying to eat it.

Non-Structural Carbohydrates and Sugars

Alongside the tough structural fiber, grass stores soluble sugars and short-chain polymers that serve as its energy reserves. In temperate grasses, these water-soluble carbohydrates include glucose, fructose, sucrose, and fructans. Their concentration is not fixed throughout the day; levels generally rise from morning to evening as the plant photosynthesizes, with daily swings of up to about 74 grams per kilogram of dry matter.⁵ This matters enormously for horse owners worried about laminitis: afternoon pasture is measurably higher in sugar than early-morning pasture.

Nitrogen fertilization pushes these sugars in the opposite direction. When a perennial ryegrass sward received more nitrogen, its water-soluble carbohydrate and fructan levels dropped significantly, while crude protein rose.⁶ In simple terms, grass that gets extra nitrogen channels its resources toward making protein rather than stockpiling sugar.

Crude Protein and Nitrogen

Grass is not usually thought of as a protein source, but young grass can be surprisingly rich in it. In native warm-season stands cut at 30-day intervals, crude protein averaged about 74 grams per kilogram of dry matter. Letting the same grass grow for 120 days before cutting dropped that to roughly 40 grams per kilogram.² Meanwhile, degraded tropical pastures that received manure saw crude protein jump from 96 to 157 grams per kilogram, showing how dramatically management can swing protein content.⁷

Not all of the nitrogen in grass is true protein. A portion exists as nitrate, free amino acids, and other non-protein nitrogen. In perennial ryegrass, higher nitrogen fertilization increased the nitrate content of herbage alongside total crude protein.⁶ For ruminants, that non-protein nitrogen can be converted into microbial protein in the rumen. For monogastric animals or humans, nitrate-rich forage is less useful and potentially harmful at very high levels.

Lipids and Fatty Acids

Fat is the smallest macronutrient fraction in grass, typically making up only about 2% to 5% of dry matter. Despite those low concentrations, the fatty acid profile is interesting. Fresh pasture grasses tend to be rich in the omega-3 fatty acid alpha-linolenic acid (ALA), which is why grass-fed beef and dairy products carry more omega-3s than grain-fed equivalents. Early research in Nature identified the fatty acid composition of pasture grass lipids as a distinct area of nutritional interest, and subsequent work has confirmed that ALA often dominates the fatty acid pool in fresh green forage.⁸ As grass matures and dries, lipid content tends to decline and the fatty acid profile shifts, which is one reason hay-fed animals produce milk and meat with a different fat profile than animals on fresh pasture.

Major Minerals in Grass

Grass contains all the major minerals that grazing animals require: calcium, phosphorus, magnesium, potassium, and sodium. But their concentrations are anything but stable. In a South African communal pasture tracked across a full year, grass phosphorus swung from about 2.4 milligrams per gram in the wet month of March down to just 0.33 milligrams per gram during the dry winter months of June and July. Even moderate rainfall was enough to trigger a rebound, with phosphorus climbing back above 1 milligram per gram within a couple of months.⁹

Calcium behaved differently in the same study. It did not track rainfall the way phosphorus did, and actually showed a significant increase in one dry-season month despite no rainfall, suggesting that plant calcium dynamics are driven more by plant physiology and soil chemistry than by immediate water availability.⁹ These seasonal swings explain why livestock managers supplement minerals during dry periods rather than relying on pasture alone.

Potassium is usually abundant in grass, often the most concentrated mineral. That abundance becomes a problem in certain conditions. High potassium in the rumen increases the electrical potential across the rumen wall, which impairs magnesium absorption. This is the primary mechanism behind grass tetany, a sometimes-fatal condition in cattle and sheep grazing lush, fast-growing pasture in spring.¹⁰ The grass itself may contain adequate magnesium, but when potassium is simultaneously high, the animal cannot absorb enough of it.

Trace Minerals

Grass also delivers trace elements including iron, zinc, copper, manganese, and selenium, though concentrations depend heavily on what the soil supplies. A study of pasture grasses under different fertilizer regimes found that increasing nitrogen and phosphorus applications caused systematic decreases in calcium, sodium, magnesium, potassium, iron, and zinc content of the grass.¹¹ That is a counterintuitive result: fertilizing more aggressively for yield can dilute the mineral density of every bite of grass an animal takes.

For grazing beef cattle, trace mineral nutrition is frequently complicated by antagonists in the forage itself. Sulfur, molybdenum, and iron in grass can tie up copper and make it biologically unavailable even when laboratory analysis says the copper concentration looks adequate.¹² Selenium is another common shortfall. Grasses grown on selenium-poor soils, which are widespread in parts of North America, eastern Europe, and China, cannot meet ruminant requirements without supplementation. This is why free-choice mineral blocks are such a standard feature of grazing operations: the grass provides a base, but rarely a complete trace-mineral package.

Vitamins and Phytochemicals

Fresh, green grass is a meaningful source of fat-soluble vitamins, especially vitamin E (as alpha-tocopherol) and provitamin A (as beta-carotene). In organic dairy herds, grass-clover silage contained about 30 milligrams per kilogram of dry matter of alpha-tocopherol and 21 milligrams per kilogram of beta-carotene, both substantially higher than maize silage, which delivered only about 13 and 8 milligrams per kilogram respectively.¹³ This is why cows on fresh pasture produce butter with a deeper yellow color and higher vitamin content than cows on conserved feeds.

Grass also contains chlorophyll, phenolic compounds, and other phytochemicals that function as antioxidants. Processed drinks made from young rice, wheat, and barley grasses contained measurable chlorophyll (82 to 958 micrograms per 200 mL serving) and total phenolic compounds with demonstrable antioxidant activity.¹⁴ Wheatgrass juice, the most popular human-consumed grass product, concentrates chlorophyll, minerals, amino acids, and antioxidants enough to be studied as a functional food for chronic disease management.¹⁵ These compounds are present in mature grass too, but harvesting at the young, vegetative stage concentrates them while keeping the indigestible fiber low enough for human consumption.

Why Maturity Changes Everything

If there is one theme running through grass nutrition, it is that maturity degrades quality. Young grass is higher in protein, lower in fiber, and more digestible. Old grass is the opposite. In native warm-season grasses, the difference between a 30-day and a 120-day harvest interval meant a drop from about 74 to 40 grams of crude protein per kilogram, while NDF climbed from 620 to 710 grams per kilogram.² Ryegrass showed the same pattern: fiber digestion rates and overall forage quality clearly declined as the plant matured.¹⁶

Range herbage in Sudan tracked to 27 weeks of age saw crude protein fall to about 4% while crude fiber ballooned and lignin hit nearly 35% of dry matter.⁴ At that point, the grass is essentially cellulose and lignin with a thin coating of nutrients. This is why rotational grazing and strategic cutting matter so much: you are not just managing yield, you are managing the nutrient density of every mouthful.

Cool-Season Versus Warm-Season Grasses

Grasses are often split into C3 (cool-season) and C4 (warm-season) types based on how they photosynthesize, and that biochemical difference shows up in their nutritional profiles. C3 grasses such as ryegrass and timothy tend to have higher foliar nutrient levels, including more protein and more soluble carbohydrates, than C4 grasses like bermudagrass and big bluestem.¹⁷

C4 grasses generally carry higher proportions of structural carbohydrates and lignin than C3 grasses at comparable maturity. Research with Korean crossbred goats found that while the specific fiber fractions varied with cultivar and harvest conditions, the C4 forages consistently showed reduced fiber digestibility compared to C3 grasses, which was attributed to a higher proportion of lignin in the fiber and to the thickened bundle-sheath cells characteristic of C4 leaf anatomy.¹⁸ In practice, this means warm-season pastures often need protein or energy supplementation to match the animal performance achievable on cool-season grass, even though C4 grasses produce more total biomass per acre in hot climates.

How Soil and Fertilizer Shape the Nutrient Profile

Grass can only deliver minerals that the soil supplies, and soil chemistry sets hard limits on what ends up in each blade. Soil pH influences the availability of phosphorus, potassium, and nitrogen to plant roots. In one controlled experiment, the available phosphorus in rhizosphere soil differed by more than fivefold between plants grown at pH 9.0 versus pH 7.2.¹⁹ While that particular study focused on a broadleaf plant, the principle holds across vegetation: the same soil can feed two adjacent fields of grass very different mineral diets if their pH differs.

Fertilizer type and rate reshape the grass nutrient profile in ways that are not always intuitive. In alpine meadow grasses, nitrogen fertilization boosted crude protein by over 20%. Potassium, zinc, boron, selenium, and molybdenum applications also raised protein content to varying degrees.²⁰ But as noted earlier, heavier nitrogen and phosphorus inputs can simultaneously dilute mineral concentrations in the grass, a phenomenon sometimes called the “dilution effect” where rapid growth outpaces mineral uptake. Manure application, by contrast, tends to improve both protein and mineral balance, likely because it returns a broad spectrum of nutrients rather than just one or two.⁷

Late-season nitrogen applications on bermudagrass increased crude protein concentrations in stolons during the dormant months from November through April, without substantially changing the carbohydrate reserves the grass needs for spring regrowth.²¹ That kind of fine-tuned management lets pasture managers front-load protein into seasons when animals need supplementation most.

Silica, Endophyte Toxins, and Other Anti-Nutrients

Grass does not hand over its nutrients without a fight. One of its signature defense strategies is depositing microscopic silica granules, called phytoliths, into its leaf blades. Grasses lack the complex chemical defense pathways of many other plant families and rely heavily on this physical deterrent instead.²² Silica wears down the teeth of grazers and reduces the digestibility of leaf tissue. Research on Serengeti grasses found that silica concentration increased with watering but not with clipping, suggesting the plant ramps up this defense when conditions favor growth rather than in direct response to herbivory.

Beyond silica, many grasses harbor fungal endophytes that produce ergot alkaloids. Perennial ryegrass and tall fescue infected with Neotyphodium endophytes have been found to contain ergovaline along with additional alkaloids including ergine, chanoclavine-I, and dehydroergovaline.²³ These compounds can cause fescue toxicosis in cattle, leading to poor weight gain, heat intolerance, and reduced milk production. The endophyte relationship benefits the grass by deterring insect herbivores, but it makes the forage less safe for livestock. Breeding programs have developed “novel endophyte” grass cultivars that retain the insect-deterrent benefits without producing the alkaloids most toxic to grazing animals.

What Young Grass Offers Humans

Humans cannot digest mature grass; we lack the rumen fermentation or hindgut capacity to break down cellulose. But harvesting grass at the very young, vegetative stage, before significant fiber accumulates, makes it possible to extract or juice the nutrient-dense cellular contents. Wheatgrass, barley grass, and oat grass are the most commonly consumed forms. A comprehensive review of wheatgrass juice described it as rich in chlorophyll, vitamins, minerals, amino acids, and antioxidants, with potential applications in managing chronic diseases and supporting overall health.¹⁵

When processed into drinks, young grasses from rice, wheat, and barley varieties delivered measurable phenolic compounds and antioxidant activity, with substantial variation across cultivars. Barley grass drinks in particular showed the highest chlorophyll content per serving among the grasses tested.¹⁴ The appeal for human consumers is that young grass concentrates many of the same vitamins and minerals present in mature forage, particularly beta-carotene, vitamin E, iron, and potassium, in a form you can actually swallow and absorb. Whether the health claims around wheatgrass extend beyond its straightforward nutrient content into therapeutic territory remains an active area of research, with most evidence still at the observational or preliminary stage rather than coming from large clinical trials.

Rumen Fermentation Turns Grass Into Something Else

For the animals that actually live on grass, the nutrients listed above are starting materials rather than end products. In the rumen of cattle and sheep, microbial fermentation converts structural and non-structural carbohydrates into volatile fatty acids, chiefly acetate, propionate, and butyrate, which the animal absorbs as its primary energy source. Studies using artificial rumen systems have confirmed that both the water-soluble and water-insoluble fractions of dried grass contribute to volatile fatty acid production, with the relative proportions varying across growing seasons.²⁴ Rumen microbes also synthesize B vitamins and convert non-protein nitrogen into microbial protein, meaning ruminants extract more total nutrition from grass than any chemical analysis of the plant itself would predict. It is one of the reasons a cow can thrive on a diet that would starve a horse of the same body weight: the rumen fermentation adds nutritional value that simply is not there in the raw plant.

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ZIRAA’AH MAJALAH ILMIAH PERTANIAN. KANDUNGAN ACID DETERGENT FIBER (ADF) DAN NEUTRAL DETERGENT FIBER (NDF) PADA RUMPUT Brachiaria humidicola PADA UMUR DEFOLIASI BERBEDA
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PubMed Central. Nutritive Value Response of Native Warm-Season Grasses to Harvest Intervals and Durations in Mixed Stands
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Open Journal of Animal Sciences. Effect of Stages of Maturity on Nutritive Value of Some Range Herbage Species in Low-Rainfall Woodland Savanna Southern Darfur, Sudan
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PubMed. Water- and Ethanol-Soluble Carbohydrates of Temperate Grass Pastures: a Review of Factors Affecting Concentration and Composition
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Agronomy Journal. Effect of fertilizer inputs on productivity and herbage quality of native pasture in degraded tropical grasslands
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Nature. Fatty acid composition of the lipids of pasture grasses
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PubMed Central. Phosphorus, calcium, and magnesium contents of pasture and their effect on body condition scores and body mass of communal cattle depending on natural pasture of Mogosane Village, of the North-West Province, South Africa
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PubMed. Impaired absorption of magnesium in the aetiology of grass tetany
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PubMed Central. Trace Mineral Nutrition of Grazing Beef Cattle
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ScienceDirect. Alfa-tocopherol and beta-carotene in roughages and milk in organic dairy herds
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PubMed Central. Chlorophyll and total phenolic contents, antioxidant activities and consumer acceptance test of processed grass drinks
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PubMed Central. Therapeutic Potential of Wheatgrass Juice: A Comprehensive Narrative Review
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Animal Feed Science and Technology. Effect of maturation and initial harvest dates on the nutritive characteristics of ryegrass (Lolium perenne L.)
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PubMed. Relative nutritional quality of C(3) and C(4) grasses for a graminivorous lepidopteran, Paratrytone melane (Hesperiidae)
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PubMed Central. Comparative Effects of C3 and C4 Forages on Growth Performance, Digestibility, and Nitrogen Balance in Korean Crossbred Black Goats
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PubMed Central. Effects of different fertilizers on nutrient quality and mineral elements in different economic forage groups in Qilian Mountain alpine meadows
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Crop Science. Influence of Three Nitrogen Fertilization Schedules on Bermudagrass and Seashore Paspalum: II. Carbohydrates and Crude Protein in Stolons
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PubMed Central. Leaf silica concentration in Serengeti grasses increases with watering but not clipping: insights from a common garden study and literature review
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NZGA: Research and Practice Series. Ergot alkaloids additional to ergovaline in endophyte-infected perennial ryegrass and tall fescue in New Zealand
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