Sudan hay is dried forage made from sudan grass (Sorghum sudanense), a warm-season annual in the sorghum family that thrives in hot, dry conditions and produces large volumes of leafy biomass for livestock feed. It sits in a middle tier of forage quality: lower in protein than alfalfa but often cheaper and easier to grow, and higher in fiber than many grain-based feeds. What makes sudan hay distinctive, and what keeps it from being a simple commodity, is a dual toxicity risk from prussic acid and nitrates that demands careful management from field to feed bunk.
What Sudan Grass Actually Is
Sudan grass originated in the upper Nile region of Africa and arrived in the United States in the early 1900s as a summer forage crop. It is classified as Sorghum sudanense (Piper) Stapf, and agronomists consider it one of the most dependable warm-season annuals for forage production because of two traits: it handles drought well, and it regrows quickly after each cutting, making multiple harvests per season possible.1THEORETICAL & APPLIED PROBLEMS OF AGRO-INDUSTRY. Assessment of adaptability and quality indicators of a new variety of Sudanese grass Basta (Sorghum × drummondii.) in the forest steppe of the Ob region of the Altai Territory Those properties make it especially attractive in arid and semi-arid regions where perennial cool-season grasses struggle to survive midsummer heat.
When people say “sudan hay,” they usually mean the cut-and-dried version of either pure sudan grass or a sorghum-sudan hybrid. Sorghum-sudan hybrids cross sudan grass with grain sorghum (Sorghum bicolor) and tend to produce thicker stems and higher tonnage per acre but coarser feed. You will see both marketed under names like “sudangrass,” “sudan-sorghum,” or “sorghum-sudangrass,” and for feeding purposes they are managed similarly, though their nutritional profiles and toxicity levels can differ by variety.
Nutritional Profile
Sudan hay’s nutritional value depends heavily on when it was cut and what variety was planted, but some general ranges hold across studies. Crude protein in sorghum-sudan hybrids harvested as hay has been measured at roughly 14 to 15 percent in higher-quality varieties, with neutral detergent fiber (the measure of total cell-wall content, which determines how much an animal can eat before feeling full) running in the mid-50s as a percentage of dry matter. Acid detergent fiber, which reflects the less digestible portion, typically falls in the low-to-mid 30s. Dry matter digestibility in those same hybrids exceeded 50 percent.2Acta Scientiarum Animal Sciences. Nutritional characteristics of sorghum hybrids hay (sorghum sudanense x sorghum bicolor)
What those numbers mean in practical terms: sudan hay is a reasonable maintenance forage for adult cattle and horses that are not in heavy production, but it usually needs supplementation for growing animals, lactating cows, or performance horses. Compared to alfalfa, which typically tests above 18 percent crude protein and has lower fiber, sudan hay delivers less punch per pound. Compared to low-quality grass hays like mature bermudagrass, it often comes out ahead in both protein and digestibility. It fills a niche as an affordable bulk forage that keeps rumen function ticking along without breaking the feed budget.
The timing of the cut shifts these numbers substantially. Young sudan grass cut at boot stage (before the seed head fully emerges) will be leafier, higher in protein, and lower in fiber. The same field left to reach full heading or maturity will produce more tonnage but a woodier, less nutritious product. Producers chasing quality over yield aim for earlier harvests and accept smaller hauls per cutting.
How Sudan Hay Is Used in Livestock Operations
Beef cattle operations are the largest consumers of sudan hay, using it as a mid-quality roughage in backgrounding and maintenance rations. A study examining cattle feeding behavior found that when animals were offered sudan grass hay alongside a high-concentrate diet, they strongly preferred the concentrate, but the hay served a critical function in buffering rumen acidity. Cattle on high-grain diets develop acidosis when their rumen pH drops too low, and the fiber in sudan hay helps prevent that by stimulating chewing and saliva production, which naturally buffers rumen pH.3PubMed Central. Cattle are more motivated for a high-concentrate diet than Sudan grass hay, despite low reticulorumen pH In other words, sudan hay often plays the role of a digestive stabilizer rather than a primary calorie source.
Sheep and goats also eat sudan-type forages, though they process them differently. Research comparing Sudan desert sheep and Nubian goats on various roughages found that sheep had higher digestibility coefficients and extracted more total digestible nutrients from the same feeds than goats did.4Asian Journal of Animal and Veterinary Advances. Utilization of High and Low-Quality Roughages by Sudan Desert Sheep and Nubian Goats That makes sense physiologically: sheep have evolved to do more with moderate-fiber grasses, while goats are better adapted to browsing shrubby, high-fiber vegetation. For small-ruminant producers, sudan hay works well for sheep but may need more protein supplementation when fed to goats.
Horse owners sometimes turn to sudan hay as a lower-calorie alternative to richer forages, especially for easy keepers prone to weight gain. It is palatable enough that most horses eat it readily, and its moderate sugar and starch content can be an advantage for metabolically sensitive animals. The caveat is the toxicity risk discussed below: horses are more sensitive to certain sorghum-related toxins than cattle, and some veterinarians advise against feeding any sorghum-family forage to horses unless it has been tested.
The Prussic Acid Problem
The most serious risk with sudan hay, and the reason it demands more caution than a typical grass hay, is prussic acid (hydrogen cyanide, or HCN). Sudan grass and all its sorghum relatives contain a compound called dhurrin, a cyanogenic glycoside stored in the plant’s cells. When the plant is damaged by frost, wilting, trampling, or chewing, enzymes break dhurrin down into prussic acid, which is acutely toxic. In grazing cattle, death can occur within minutes of consuming a lethal dose.5PubMed Central. A comparison of Dhurrin-free and conventional varieties of sorghum sudangrass baleage
Prussic acid poisoning works by blocking the ability of cells to use oxygen, essentially suffocating the animal from the inside out even though it is still breathing. Symptoms include labored breathing, staggering, convulsions, and bright cherry-red blood (because the blood is carrying oxygen but the cells cannot accept it). The speed of onset is what makes this poison so feared: by the time an owner notices an animal in distress, treatment may already be too late.
Several factors push prussic acid levels higher in the living plant. Heavy nitrogen fertilization increases both prussic acid and nitrate concentrations in sudan grass.6Agronomy Journal. Influence of Nitrogen Fertilization and Other Factors on Yield, Prussic Acid, Nitrate, and Total Nitrogen Concentrations of Sudangrass Cultivars Young, rapidly growing plants after a rain following drought stress are especially dangerous, as regrowth tissue concentrates dhurrin. Short plants under about 18 to 24 inches are generally riskier than taller, more mature growth.
Why Hay Is Safer Than Grazing, but Not Foolproof
One of the main reasons producers make sudan grass into hay rather than grazing it directly is that the drying process dissipates a substantial portion of the prussic acid. HCN is a volatile gas, and as the cut forage wilts and cures in the field, much of it escapes into the air. By the time sudan grass has been properly dried, raked, and baled, prussic acid levels are dramatically lower than they were at cutting. This is well understood in the sorghum forage world and is the primary reason haymaking is considered a safer way to feed sudan grass than fresh grazing.
Ensiling offers a similar benefit. Research on sorghum cultivars at various growth stages found that HCN levels in the plant material dropped during the ensiling process, with forage sorghum silages approaching zero parts per million.7Agronomy Journal. Effects of Ensiling on the Hydrocyanic Acid Potential of Sorghum Plants The fermentation environment, combined with the time the forage spends sealed in the silo or bag, allows the volatile HCN to break down or escape. For producers who make baleage (a form of ensiled hay wrapped in plastic), this is reassuring, though the degree of reduction depends on the cultivar and growth stage at harvest.
Still, “safer” does not mean “zero risk.” If sudan grass is cut during a period of very high dhurrin accumulation (say, young regrowth heavily fertilized with nitrogen after a drought-breaking rain), even baled hay can retain enough prussic acid to cause problems, especially if the hay was baled before it was fully cured. And hay that gets rained on and rewetted during field curing can trap HCN that would otherwise have dissipated. Testing is the only way to be sure, and many university extension labs offer HCN testing for sorghum forages for a modest fee.
Nitrate Toxicity, the Other Risk
While prussic acid gets the headlines, nitrate accumulation in sudan hay is arguably a more common day-to-day management challenge. All plants take up nitrate from the soil, but sorghum-family grasses are particularly efficient at it, and under certain conditions they accumulate far more than they can convert into protein. When livestock eat that high-nitrate forage, microbes in the rumen convert nitrate to nitrite, which enters the bloodstream and interferes with hemoglobin’s ability to carry oxygen. The result, methemoglobinemia, presents similarly to prussic acid poisoning: labored breathing, weakness, and potentially death, though it typically develops more slowly.
The conditions that drive nitrate accumulation overlap with the conditions that drive prussic acid risk but are not identical. Heavy nitrogen fertilization is a major factor, as each additional unit of nitrogen applied to the field increases the plant’s nitrate concentration.6Agronomy Journal. Influence of Nitrogen Fertilization and Other Factors on Yield, Prussic Acid, Nitrate, and Total Nitrogen Concentrations of Sudangrass Cultivars Drought stress stalls the plant’s metabolism, allowing nitrate to pile up in the stems without being converted to amino acids. Overcast, cool weather has a similar effect. And unlike prussic acid, nitrate does not volatilize during hay curing. Whatever nitrate was in the plant at cutting stays in the bale. This makes testing particularly important for sudan hay harvested from heavily fertilized fields or during drought conditions.
Nitrate concentrations are highest in the lower stems and lowest in the leaves. Cutting height matters: a higher stubble height leaves more of the nitrate-rich stem base in the field rather than in the bale. Some producers test individual bales from the same field and find significant variation, because soil fertility, drainage, and microtopography all create patchwork differences in uptake across even a single cutting.
As a general guideline, hay testing below about 0.5 percent nitrate (on a dry matter basis, sometimes reported as nitrate-nitrogen at about 1,000 ppm) is considered safe for all classes of livestock. Levels between 0.5 and 1.0 percent are cautionary and may be fed if diluted with other forages. Above 1.0 percent, the hay is dangerous and should either be blended carefully at low inclusion rates or discarded. Pregnant animals are especially vulnerable to nitrate poisoning and should never be fed untested sudan hay from a questionable field.
Growing Conditions and Why They Matter to the Buyer
If you are buying sudan hay rather than growing it, you might wonder why the growing conditions matter to you. The answer is that a bale’s safety and quality are baked in long before it arrives at your barn. Sudan grass is a heavy nitrogen user, and research on irrigation management has shown that applying around 200 kilograms of nitrogen per hectare optimized growth, biomass, and water use efficiency, while more severe water deficits actually increased nitrogen concentration in the plant tissue.8Irrigation and Drainage. Water Deficit Irrigation and Nitrogen Response of Sudan Grass under Arid Land Drip Irrigation Conditions A producer pushing for maximum yield with heavy fertilizer applications and limited irrigation is, in effect, engineering a crop that will test higher for both nitrate and prussic acid.
When sourcing sudan hay, the questions worth asking your supplier are straightforward: How much nitrogen was applied? Was the crop stressed by drought before cutting? How tall was the stand at harvest? Was the hay tested? Producers who routinely test their crop and can show you a forage analysis are the ones to buy from. The analysis should include crude protein, fiber fractions, and ideally both nitrate and HCN levels. Without that test, you are guessing, and with sudan hay, guessing is riskier than with most other forages.
Sorghum-Sudan Hybrids and Variety Differences
Most sudan hay sold today comes not from pure sudan grass but from sorghum-sudan hybrids, which combine sudan grass’s fine stems and leafiness with grain sorghum’s higher tonnage. These hybrids vary considerably in their nutritional profiles. Evaluated hybrids have shown crude protein ranging from roughly 10 to over 15 percent depending on the specific cross, with the best performers delivering both high protein and relatively lower fiber.2Acta Scientiarum Animal Sciences. Nutritional characteristics of sorghum hybrids hay (sorghum sudanense x sorghum bicolor) For producers planting their own, variety selection is one of the highest-leverage decisions they can make, since it determines the ceiling on quality before any management factor comes into play.
Breeding programs are now actively developing low-dhurrin or dhurrin-free sorghum-sudan varieties, specifically to reduce prussic acid risk. Early evaluations of these lines are underway, comparing dhurrin-free varieties against conventional ones in both baleage and hay form.5PubMed Central. A comparison of Dhurrin-free and conventional varieties of sorghum sudangrass baleage If these varieties prove commercially viable and maintain acceptable yields, they could eventually take much of the toxicity anxiety out of sudan-type forages. That said, dhurrin-free genetics address only one of the two major toxicity risks. Nitrate accumulation is a function of soil nitrogen and plant physiology, not cyanogenic glycoside genetics, so low-dhurrin varieties would still need nitrate testing under risky growing conditions.
Feeding Sudan Hay to Horses
Horses occupy an unusual place in the sudan hay conversation. While cattle and sheep can tolerate moderate levels of sorghum toxins because their rumen microbiome partially detoxifies certain compounds, horses lack a rumen entirely. They are hindgut fermenters, which means toxic compounds from sorghum forages can pass into the bloodstream without the same microbial processing that cattle benefit from.
Beyond prussic acid, horses fed sorghum-family forages have historically been associated with a condition called equine sorghum cystitis, which involves degeneration of nerve tissue controlling the bladder and hind limbs. Affected horses develop urinary incontinence and hindquarter weakness. The condition is most strongly linked to grazing fresh sorghum or sudan grass rather than eating cured hay, but the association has made many equine veterinarians cautious about any sorghum product in horse diets. If you do feed sudan hay to horses, a clean forage analysis showing low HCN and nitrate levels is essentially non-negotiable, and many horse owners simply choose to avoid the category altogether.
Comparing Sudan Hay to Other Common Forages
Where sudan hay fits in the forage landscape depends on what you are comparing it to and what your animals need. Against cool-season grass hays like timothy or orchardgrass, sudan hay is typically comparable in protein and fiber when both are harvested at a similar maturity stage. Its advantage is that it grows in summer heat when cool-season grasses have gone dormant, filling a seasonal gap in forage production. Against alfalfa, sudan hay loses on protein and energy density but wins on cost per ton in most markets and avoids the risk of bloat that legume hays carry for cattle.
Against other warm-season annual forages like pearl millet, sudan hay’s main distinction is the toxicity burden. Pearl millet does not produce dhurrin and poses no prussic acid risk, which is why it has gained market share in areas where sorghum cyanide concerns are a major issue. However, pearl millet generally yields less biomass per acre and does not tolerate drought quite as well as sudan grass, so the tradeoff is real. Teff grass is another warm-season alternative that has become popular in the horse market specifically because it has no known toxicity issues, but it yields less and costs more.
For cattle operations with the infrastructure to test forage and manage risk, sudan hay remains one of the most cost-effective warm-season roughages available. For horse operations or situations where testing is impractical, the alternatives mentioned above offer peace of mind at some cost in yield or price.
Storage and Shelf Life Considerations
Sudan hay stores much like other grass hays, with one important caveat. Because prussic acid is volatile, a well-cured bale that sits in dry storage for several months will generally have lower HCN levels than it did at baling. Time is your ally for prussic acid. Nitrate, by contrast, is stable: a bale that tested high for nitrate at baling will still test high a year later. There is no aging out of nitrate risk.
Moisture at baling matters more for sudan hay than for many other forages, both for mold prevention and for toxin management. Baling at above 18 to 20 percent moisture invites mold growth in any hay, but with sudan hay it also traps HCN that would otherwise have escaped during further curing. Producers who bale on the dry side and store under cover produce the safest product. Hay stored outdoors uncovered in humid climates will absorb moisture, encouraging both mold and the retention of any residual prussic acid. If you receive sudan hay that smells musty or shows visible mold, the concern is not just spoilage but the possibility that the bale never cured properly in the first place, which raises questions about what else might still be lurking inside.