Nutrients in Hay Explained: Fibre, Protein and More

Hay is the foundation of most horses' diets for much of the year, yet the nutrients in hay are the part of the ration owners understand least. The American Association of Equine Practitioners puts hay at 50 to 90 per cent of a normal, healthy horse's daily nutritional needs (Kim F. Miller and Dr Meriel Moore-Colyer, AAEP, May 2025), so what is in the bale matters more than what is in the bucket. This guide explains what hay actually contains, how much those nutrients vary from bale to bale, how to read a hay analysis line by line, and where popular advice on soaking, steaming and "low-sugar" hay goes further than the research does.

It is written for owners in the UK and South Africa, so it covers British meadow and seed hays as well as the teff, eragrostis, oat hay and lucerne that fill South African feed rooms. Energy is given in megajoules, as in the European research cited here, rather than the American megacalorie.

What Are the Main Nutrients in Hay?

Does hay have any nutritional value? A great deal. Hay is grass or legume cut and dried, and it carries every class of nutrient a horse needs apart from water. The British Horse Society's feeding guidance names five major nutrients: water, fibre, carbohydrates, fats and protein. Hay supplies four of those, plus minerals and some vitamins.

Nutrient	What it does for the horse	How a hay analysis reports it
Fibre	Keeps the gut moving and is fermented in the hindgut for energy and heat (BHS)	Neutral detergent fibre (NDF), acid detergent fibre (ADF), crude fibre
Sugars and starch	Quick-release energy, and the fraction that matters for laminitis risk	Water-soluble carbohydrate (WSC), ethanol-soluble carbohydrate (ESC), starch, non-structural carbohydrate (NSC)
Protein	Growth and repair (BHS)	Crude protein (CP)
Fat	Helps the absorption of nutrients (BHS); hay carries little of it	Oil or ether extract
Energy	The total the horse can extract from all of the above	Digestible energy (DE), in MJ per kg of dry matter
Minerals	Bone, muscle, nerve and enzyme function	Ash, plus individual minerals if you order them
Vitamins	Antioxidant and metabolic roles	Request separately if you need a figure

Fibre is by far the biggest share. In Feedipedia's oat hay tables (the feed database run by INRAE, CIRAD, AFZ and the FAO), neutral detergent fibre averages 61.7 per cent of dry matter against 9.1 per cent crude protein and 2.2 per cent oil. Hay is mostly fibre with a smaller, highly variable package of everything else, and it is that variable package that decides whether a particular hay suits your horse.

Why the Nutrients in Hay Vary So Much

No two hays are the same, and the differences are bigger than most owners assume. When Julliand and colleagues analysed 21 hays from 15 French departments (Animal, 2019, PMID 30719961), digestible energy ranged from 6.77 to 9.66 MJ per kg of dry matter and crude protein from 63 to 160 g per kg. The authors did the arithmetic: a 500 kg horse eating 10 kg of hay dry matter a day would see a 20 MJ daily difference from a 2 MJ/kg gap between two hays, which they put at around 30 per cent of that horse's maintenance energy requirement. Two bales that look much alike can be the difference between a horse holding condition and slowly losing it.

Cutting Date and Plant Maturity

The stage the crop reaches before it is cut has the biggest single effect. The University of Georgia's equine programme (Allison Bailey, October 2025) explains that young, leafy plants carry more protein and less fibre, and puts the best harvest point for grasses at the boot to early-head stage and for lucerne and clover at early to mid-bloom. As plants mature, stems thicken and fill with cellulose, hemicellulose and lignin, which the horse digests less well.

A Scandinavian trial measured exactly how much this matters (Stang and colleagues, Journal of Animal Science, 2023, PMID 36576899). Six grass species were cut on three dates between early June and early July. In general, crude protein fell and fibre rose as the grasses matured, and harvest time had a larger effect on digestibility than which grass it was. Sugar did not behave so tidily. Water-soluble carbohydrate "varied to a large extent": it rose with maturity in timothy and smooth bromegrass, fell in cocksfoot, and fructans increased in four of the six species as they aged.

That finding matters to anyone feeding a laminitis-prone horse. A late-cut, stalky hay is reliably lower in protein and digestibility, but it is not reliably lower in sugar. Only an analysis tells you which way your batch went. If you make your own, our guide to making hay for horses covers cutting and baling in a British summer.

Grass Species, Soil and Management

Species sets the baseline. The MSD Veterinary Manual (Nettie R. Liburt, feeding practices, February 2026) says warm-season grasses such as teff and Bermuda grass are "consistently lower in starch, sugars, and fructans" than cool-season hays such as timothy, cocksfoot (orchard grass) and brome, but can be short of calcium or high in oxalates that interfere with calcium uptake. Legumes and legume-grass mixtures, it adds, generally carry more protein, minerals and vitamins than grass hays alone.

Management can surprise you. A Belgian trial compared hay from a species-rich sward that had received no mineral fertiliser for ten years with hay from intensively managed perennial ryegrass (Fiems and colleagues, Archives of Animal Nutrition, 2004, PMID 15264672). The unfertilised hay had 32 per cent less protein and 35 per cent less ash, yet 117 per cent more water-soluble carbohydrate. Two caveats belong with that result: the ryegrass hay was of low to moderate quality because of poor weather, and the hays were fed to cattle and sheep, not horses. The lesson is still a useful one. A "natural", unimproved meadow hay is not automatically a low-sugar hay.

Minerals follow the soil the crop grew on. If you grow your own forage, the soil-testing section of our paddock care guide explains how to find out what your ground is short of before it shows up in the bales.

Weather and Storage

A Horse & Hound feed forum piece on forage quality makes the point that hay quality depends on storage after baling as well as the weather at cutting. It advises leaving small spaces between newly baled hay so that air can move round the bales, because without them the stack can heat and grow mould, leaving bales that are matted and musty. Storage also costs vitamins, which is covered further down.

How to Read a Hay Analysis

A hay analysis for horses looks intimidating at first, but every report is built from the same handful of lines. Once you know what each one measures, you can compare two hays in a couple of minutes.

As Fed Versus Dry Matter

Most reports show two columns. "As fed" (or "as sampled") describes the hay as it arrived, water included. "Dry matter" describes the same sample with all the moisture removed. Always compare hays on the dry matter column, because water dilutes every other figure.

Well-made hay is mostly dry matter. The MSD Veterinary Manual describes dried hays as more than 88 to 90 per cent dry matter, the AAEP says a bale harvested at its nutritional peak should be 85 per cent dry matter, and the University of Georgia gives 10 to 17 per cent moisture as safe for storage. Haylage is much wetter: the Horse & Hound feed forum gives 60 per cent dry matter as normal. That is why, as the BHS points out, haylage has to be fed in larger quantities than hay to deliver the same nutrients.

A quick worked example: 10 kg of hay at 88 per cent dry matter supplies 8.8 kg of dry matter. The same 10 kg of haylage at 60 per cent supplies 6 kg.

Digestible Energy: How Many Calories Are in Hay?

This guide gives digestible energy (DE) in megajoules per kilogram of dry matter (MJ/kg DM), the unit used in the European research cited here. One megajoule is about 239 kilocalories, the "calories" of human food labels. On the range Julliand's team measured, a kilogram of hay dry matter supplies roughly 1,620 to 2,310 kcal of digestible energy. If you are reading an American source that quotes megacalories per pound, 1 Mcal/lb is about 9.2 MJ/kg.

Do not confuse DE with gross energy, which some tables also print. Gross energy is everything that burns in a laboratory calorimeter, including fibre the horse cannot fully digest, so it is always much higher. Feedipedia gives oat hay a gross energy of 18.0 MJ/kg DM, nearly twice the top of the digestible range above.

Crude Protein

Crude protein is calculated from the nitrogen in the sample. The University of Georgia notes that it tells you how much protein is present, not its quality. The protein section below gives the ranges to expect.

NDF and ADF

These two fibre measurements answer different questions. In the University of Georgia's definitions, neutral detergent fibre (NDF) is the whole cell wall (hemicellulose, cellulose and lignin) and reflects how much hay a horse will eat, with higher NDF meaning lower intake. Acid detergent fibre (ADF) is the least digestible portion (cellulose and lignin) and reflects digestibility, with higher ADF meaning less of the hay is digested.

WSC, ESC, Starch and NSC

These are the lines that matter most for a horse at risk of laminitis. Ethanol-soluble carbohydrates (ESC) and water-soluble carbohydrates (WSC) both measure simple sugars such as glucose and fructose. The difference is that WSC also captures fructans, the storage carbohydrates grasses build, while ESC does not. Starch is measured separately. Non-structural carbohydrate (NSC) is the combined sugar and starch fraction, the part the University of Georgia describes as likely to raise blood glucose and insulin. If the report does not print an NSC figure, ask the laboratory for it, or for both WSC and starch.

Ash and Individual Minerals

Ash is what remains when a sample is burnt: the total mineral content. It tells you nothing about which minerals are present, so if you need calcium, phosphorus, magnesium, copper, zinc or selenium figures, order them by name. Feedipedia puts oat hay ash at 8.3 per cent of dry matter on average.

Report line	What it tells you	Named benchmark
Dry matter	How much of the bale is feed rather than water	Dried hay more than 88-90% (MSD); about 85% at baling (AAEP)
Digestible energy	Energy the horse can use	6.77-9.66 MJ/kg DM across 21 French hays (Julliand 2019)
Crude protein	Protein, estimated from nitrogen	Mature horses 8-10% of the total ration; growing horses 14-16% (MSD)
NDF	Bulk; how much will be eaten	Higher means lower intake (University of Georgia)
ADF	Digestibility	Higher means less digestible (University of Georgia)
NSC	Sugar and starch load	Below 10% for horses with insulin dysregulation (ECEIM consensus)
Calcium to phosphorus	Bone and skeletal balance	Above 1:1 for all horses (MSD)
Zinc to copper	Trace mineral balance	Nutritionists commonly formulate 3:1 to 4:1 (MSD)

Protein in Hay: Which Hay Has the Most?

Legume hays lead on protein. The University of Georgia gives typical crude protein ranges of 16 to 22 per cent for legumes such as lucerne (alfalfa) and clover, 10 to 16 per cent for cool-season grasses such as timothy, cocksfoot and tall fescue, and 8 to 12 per cent for warm-season grasses. Those are typical ranges, not guarantees: the 21 French hays in Julliand's study ran from 6.3 to 16 per cent, and the UK hays Longland's team tested in 2011 averaged just 5.9 per cent (range 3 to 8.6 per cent).

For oat hay protein content, a common question from South African owners, Feedipedia's tables give an average of 9.1 per cent of dry matter with a range from 4.9 to 14.7 per cent across 35 samples. Feedipedia notes that oat hay's low protein usually needs topping up with a legume such as lucerne, that it is best cut at the soft dough stage, and that horses tend to pick out the grain heads and leave the stems. Teff behaves like other grasses: when Staniar and colleagues cut it at three stages of maturity (Journal of Animal Science, 2010, PMID 20581289), crude protein fell as it matured.

How much protein does a horse need? The MSD Veterinary Manual puts mature horses at 8 to 10 per cent of the total ration and growing horses at 14 to 16 per cent. Horses over 20 may need intakes closer to those of horses in light to moderate work, though MSD advises that liver and kidney function be checked before protein is increased. Our guide to feeding senior horses covers the rest of the older horse's diet.

Higher is not automatically better. A youngster, a lactating mare or a horse in hard work can use the protein and energy in lucerne (alfalfa) hay, but the University of Georgia warns that legumes fed on their own can be too nutrient-dense for easy keepers and horses with metabolic problems.

In South Africa, much lucerne is sold on a grade. The National Lucerne Trust's Hay Quality and Grading Scheme grades lucerne with near-infrared (NIR) instruments, and its quality index uses acid detergent fibre, ash and lignin, with a Supreme category added at the top of the scale (Farmer's Weekly, February 2022). If you buy lucerne by the load, ask whether it was graded under the scheme.

Fibre in Hay and Why Horses Need It

Does hay have fibre? Hay is mostly fibre, and that is its main job. The BHS explains that horses evolved to eat little and often, chewing for up to 18 hours a day. Chewing produces saliva, which buffers the acid the stomach secretes continuously and so reduces the likelihood of gastric ulceration. Fibre fermented in the hindgut also generates heat, which the BHS describes as an in-built heating system, and the BHS links a forage-based diet to a lower risk of colic.

The BHS counts hay, haylage, grass and chaff as forage, and says forage should form the basis of every horse's diet. For a horse that needs the chewing time but not the calories, the fibre-rich end of the hay spectrum is useful. Dengie's senior nutritionist Katie Williams, quoted in 2010 in Horse & Hound, notes that coarse, stalky hay is lower in nutrients but can be useful for good doers and overweight horses, because "they can be given more of this type of hay without consuming too many calories". The BHS suggests straw as a partial hay replacement for horses with good teeth, introduced slowly, with a balancer to cover vitamins and minerals. Our guide to hay alternatives covers chopped forages, cubes and other substitutes when hay runs short.

Sugar and Starch in Hay

Carbohydrate figures matter enormously for any horse with a metabolic problem. The driver of laminitis risk in these horses is the insulin-raising, non-structural part of the carbohydrate: the simple sugars and starch.

Why NSC Matters for Laminitis, EMS and PPID

The European College of Equine Internal Medicine's consensus statement on equine metabolic syndrome (Durham and colleagues, Journal of Veterinary Internal Medicine, 2019, PMID 30724412) recommends forage with an NSC below 10 per cent "to limit postprandial insulin responses in horses with ID" (insulin dysregulation). It also states that haylage is not recommended for these horses, because insulin responses to haylage are greater than to hay of the same NSC content. The BHS feeding page gives a similar line, saying forage under 10 to 12 per cent sugar and starch is usually safer for horses that are overweight, have EMS or are prone to laminitis. Plenty of UK hay sits above that line: the hays in Longland's 2011 study started at 123 to 230 g/kg dry matter of water-soluble carbohydrate (12 to 23 per cent), and Moore-Colyer's five dry hays averaged 126 g/kg.

If your horse has had laminitis, is being managed for obesity and equine metabolic syndrome, or has Cushing's disease (PPID), the NSC line on the analysis is the most important number on the page. Agree the target with your vet.

Can You Spot Low-Sugar Hay by Looking?

No. The Scandinavian harvest-time trial found sugar moving in different directions in different grasses as they matured, and the Belgian trial found an unfertilised meadow hay with more than twice the sugar of intensive ryegrass. Coarse, stemmy hay is lower in energy, but that is not the same as lower in sugar.

Warm-season grasses are the one broad exception, according to MSD. In Staniar's teff trial, run with six Quarter Horse mares, NSC rose from 5.4 per cent at the boot stage to 8.4 per cent at late heading and stayed below 10 per cent of intake at every maturity. That teff was grown in Pennsylvania, though, and South African teff and eragrostis still need testing on their own merits.

Oat hay needs particular care if it carries grain. Feedipedia lists an oat hay starch content of 17.7 per cent of dry matter, though from only two samples, and grain heads are where the starch sits.

Does Soaking Hay Remove Sugar?

Soaking removes some sugar, but by an amount nobody can predict for your bale, which is why the question of how long to soak hay to remove sugar has no safe single answer. The research:

• Longland and colleagues (Veterinary Record, 2011, PMID 21652661) soaked UK hays that started at 123 to 230 g/kg dry matter WSC for up to 16 hours at 8°C. They lost a mean 27 per cent of their water-soluble carbohydrate, with a range from 6 to 54 per cent, and seven were still above the 100 g/kg dry matter ceiling suggested for laminitic animals afterwards. Crude protein did not change significantly.
• A follow-up (Longland and colleagues, Veterinary Record, 2014, PMID 24336793) found warm water leaches more than cold: over 16 hours, four UK hays lost 28 per cent of their WSC at 8°C and 46 per cent at 16°C. The authors cautioned that very prolonged soaking in warm water might encourage unwanted micro-organisms.
• In a UK trial at the Royal Agricultural University (Moore-Colyer and colleagues, PLOS ONE, 2014, PMID 25426729), soaking five UK hays for 9 hours at 16°C brought WSC down to 79-83 g/kg dry matter from 126 g/kg in the dry hay, with protein and ash unchanged. Soaking also raised bacterial counts more than fivefold.
• A German study of meadow hay soaked at 20°C (Bochnia and colleagues, Journal of Equine Veterinary Science, 2021, PMID 33993927) found that just 15 minutes significantly reduced nearly all the nutrients measured, including sugars, fructans, major minerals and trace elements. Longer soaking did not wash out more. Metabolisable energy fell by 5 to 15 per cent, and the protein digestible in the small intestine by 35 per cent. That sits uneasily with the UK trials, which found crude protein unchanged; the German team measured the digestible fraction rather than the total, and the two results have not been reconciled.
• In Canada, a 30-minute soak lowered soluble protein, NSC and potassium, and 13 Standardbred racehorses ate less of the soaked hay and spent less time eating it (Owens and colleagues, Journal of Animal Science, 2019, PMID 31400277).

The practical answer is to have the hay analysed. The ECEIM consensus accepts that soaking may be needed to reach its 10 per cent target in many cases, but no soak time can promise a safe sugar level. If the number matters for your horse, test the hay. If you soak, remember that you may also be washing out minerals and some of the protein's value, and that soaking raises bacterial counts.

Does Steaming Hay Reduce Sugar?

Not reliably. In the Royal Agricultural University trial, 50 minutes in a Haygain steamer left WSC at 122 g/kg dry matter against 126 g/kg in dry hay, which was not a significant difference. In the Canadian study, 60 minutes of steaming did not lower NSC. A US study that steamed two hays for 90 minutes (Earing and colleagues, Journal of Animal Science, 2013, PMID 24146155) cut WSC by 13 per cent and ESC by 27 per cent in the mouldier hay but had no effect on the other, and it reduced phosphorus by 16 to 17 per cent in both. Steaming is a hygiene tool, not a sugar tool.

Minerals in Hay

Mineral content tracks the soil the crop grew in. If a mineral is in the ground it will usually appear in the hay, and if the ground is short of it, good haymaking will not put it there. That is why a mineral analysis of your own forage is worth more than any table of averages.

Calcium and Phosphorus

The ratio between these two matters more than either figure alone. The MSD Veterinary Manual says that for all horses the calcium to phosphorus ratio should be kept above 1:1, and that requirements for both are much greater during growth than for maintaining a mature horse. Lucerne is naturally rich in calcium. Grain and bran tip the balance the other way: MSD notes that wheat and rice bran are very high in phosphorus and low in calcium, so a calcium source is needed when bran is fed.

Grass hays vary. Staniar's teff had a calcium to phosphorus ratio of about 2:1 at every maturity, and Feedipedia's oat hay averages 4.7 g of calcium and 2.0 g of phosphorus per kg of dry matter. MSD's caution about warm-season grasses still applies, though: they can be short of calcium or high in oxalates, and MSD does not recommend them for lactating mares or fast-growing youngstock unless calcium and protein are supplemented, which a ration balancer does easily.

Copper, Zinc and Selenium

Kathy Carter's 2015 Horse & Hound feature presents forage analysis partly as a way to avoid the mineral deficiencies that can arise when commercial supplements are fed alongside untested hay. Guesswork can do harm in the other direction too. MSD says nutritionists commonly formulate rations with a zinc to copper ratio of 3:1 to 4:1, and warns that excessive trace mineral intake can be as harmful as a deficiency. Very high copper may reduce the absorption of selenium and iron. At the other extreme, MSD records that zinc intakes above 1,000 ppm, from forage contaminated by environmental pollution, have induced copper deficiency and developmental orthopaedic disease, the group of growth disorders that includes osteochondrosis (OCD), in young horses.

Selenium depends almost entirely on the soil. MSD describes regions where acidic soils are profoundly selenium-deficient and others where alkaline soils produce forage with toxic levels, and the margin between enough and too much is narrow. Vitamin E and selenium work together, and a 2025 review (Finno and McKenzie, Veterinary Clinics of North America: Equine Practice, PMID 39893124) explains that prolonged deficiency of either can lead to profound clinical disease, and its subject is the muscle disease that results. Muscle damage is not always obvious: in subclinical myopathy the muscle is damaged but the horse looks normal. The same review says deficiency can usually be established from the diet and a blood test. That is the right order: test first, then supplement on your vet's advice.

Low selenium on a blood test is not the same as disease. In a Cornell review of 271 hospitalised horses (Streeter and colleagues, Equine Veterinary Journal, 2012, PMID 23447875), white muscle disease was concentrated in foals under 30 days old with low selenium. Low selenium was common in adult horses, but nutritional myopathy in adults was rare.

Sodium, Potassium and Magnesium

Hay will not cover a horse's salt needs. MSD states plainly that "sodium is not found in notable concentrations in forages", so a free-choice salt source is recommended. Working horses lose sodium, chloride and potassium in their sweat, which is hypertonic, and the dried residue of a sweat mark is partly that salt leaving the body.

Potassium is the opposite case. MSD says a ration that is at least half roughage provides more than enough potassium for a horse at maintenance, and that soaking forage leaches potassium out as well as sugar. The one group for whom high-potassium hay is a real problem is horses with hyperkalaemic periodic paralysis (HYPP), whose potassium intake MSD says must be restricted; for them an analysis is essential. Horse & Hound's feed forum also suggests that forage for performance horses be tested for calcium, phosphorus, magnesium and sodium.

Vitamins in Hay and What Storage Does to Them

Vitamins are the nutrients that suffer most between the field and the feed room, and vitamin E is the clearest example. A Belgian study of feeds on organic farms (Beeckman and colleagues, Journal of Animal Physiology and Animal Nutrition, 2010, PMID 20050949) found hay averaged 4.5 mg of vitamin E per kg of dry matter, against 52 mg in grass-clover silage and about 156 mg in fresh ryegrass. On those figures, hay carried less than a thirtieth of the vitamin E of fresh ryegrass.

The MSD Veterinary Manual says vitamin E deficiency is most likely to appear in foals nursing mares on dry winter pasture and in horses fed only low-quality hay without a fortified feed or a vitamin E supplement, and that horses without access to fresh pasture may need supplementing. The most serious consequence is neurological. In a Cornell experiment (Divers and colleagues, American Journal of Veterinary Research, 2006, PMID 16426221), eight horses kept on a dirt lot with no pasture, fed grass hay that had been stored for a year and a concentrate low in vitamin E, all saw their plasma vitamin E fall, and four developed equine motor neuron disease (EMND). None of the 51 control horses did.

Grazing is not a complete guarantee. An Edinburgh-led study of 32 European EMND cases (McGorum and colleagues, Equine Veterinary Journal, 2006, PMID 16411586) found 13 had part-time or full-time access to grass, and all of those had low vitamin E status. If you are worried, ask your vet about a blood test rather than guessing.

Lucerne brings other vitamins with it: the AAEP describes it as relatively high in energy, protein, calcium and vitamin A.

Clean Hay Matters as Much as Nutrients

Nutrient value and hygienic quality are two separate things, and they are constantly confused. The AAEP article by Miller and Moore-Colyer warns that hay with a good analysis can still carry dust, mould, fungi, bacteria and other allergens, often at a particle size of around 5 microns, roughly a tenth the width of a human hair and small enough to reach deep into the lungs. The human eye cannot see particles below about 40 microns, so the most important contaminants are invisible. This is why hay that analyses well can still trigger severe equine asthma, or heaves.

Your nose is the first check. Horse & Hound advises that a musty smell can mean a high mould content from baling or storing the hay wet, and names Aspergillus as one of the three main fungi found in stables and a suspected major cause of equine respiratory problems.

Steaming is very good at the mould part of the problem. In the Royal Agricultural University trial, 50 minutes of steaming cut mould from 1,148 to 2 colony-forming units per gram of dry matter, while soaking left mould statistically unchanged and pushed bacteria up. The most effective treatment for both sugar and microbes was soaking followed by steaming. The US study found steaming reduced mould by at least 91 per cent.

What steaming does for an asthmatic horse's lungs is less clear-cut. In a French trial (Orard and colleagues, BMC Veterinary Research, 2018, PMID 30442129), steaming significantly reduced mould but "inconsistently influenced the respiratory response" of severely asthmatic horses. A Montreal trial (Symoens and colleagues, Equine Veterinary Journal, 2025, PMID 39164027) found steamed hay improved lung function in the first two weeks, while alfalfa pellets did better over four. The same group then fed steamed hay to asthmatic horses in remission for four weeks and saw a mild deterioration in lung function and airway inflammation, no different from dry hay (Raïsky and colleagues, Equine Veterinary Journal, 2026, PMID 40923556). For a horse with asthma, steamed hay is a help, not a cure, and it belongs inside your vet's management plan.

One more hygiene point from MSD: large round bales fed in the field decompose where they touch the ground, which raises the risk of botulism and wastes a good deal of hay.

Judging Hay Quality Without a Laboratory

Analysis is ideal, but your senses tell you more than you might think, within limits. In Julliand's 2019 study, 54 non-expert volunteers sorted the 21 hays by appearance, smell and texture. Digestible energy and ADF tracked how people grouped the hays on all three senses, while crude protein and non-fibre carbohydrate (which includes the sugars) registered through appearance only. In short, your eyes, nose and hands can roughly rank a hay for energy and fibre. That is not precise enough to feed a laminitis-prone horse on, which is what the analysis is for.

Use the checks the University of Georgia and Horse & Hound describe:

• Look. Good hay is usually a pleasant, light green without being weedy. Beige can mean heat damage and brown can mean the crop was too moist when baled. White, black or other discoloured patches may be mould, and mouldy hay should not be fed.
• Smell. Fresh hay smells sweet. A musty or sour smell suggests mould.
• Feel. Leafy hay is better, because leaves carry more nutrients than stems. Stemmy hay is typically less digestible.
• Check for contaminants. Hay should be free of weeds, dust and foreign material. Defra's code of practice on ragwort warns that cut and dried ragwort remains toxic and is more likely to be eaten, which makes ragwort poisoning a hay risk as much as a grazing one.
• Shake a section. Pull a flake apart in good light and look for a dust cloud, then repeat from the middle of a few bales, not just the outside.

How to Get Your Hay Tested in the UK and South Africa

Testing is the only way to know what you are feeding. The BHS notes that you can send a sample to a feed company for nutritional analysis and that the company will discuss the results with you.

1. Sample many bales, not one. The University of Georgia recommends core sampling 10 to 20 bales per lot and mixing the cores, because quality varies even within one cutting. TopSpec's Nicola Tyler, quoted in a 2015 Horse & Hound feature by Kathy Carter, describes a 500 g sample, ideally from multiple bales, sealed in a polythene bag and sent to an accredited laboratory.
2. Test each batch separately. Horse & Hound's feed forum advises analysing first and second cuts separately because their nutritional value differs. The same goes for every new load from a different field.
3. Order the right package. For hay and haylage, Horse & Hound suggests crude protein and fibre, plus water-soluble carbohydrate for sugar; calcium, phosphorus, magnesium and sodium for performance horses; and copper, zinc, manganese and selenium for growing horses. For a horse with insulin dysregulation, make sure the report gives NSC or both WSC and starch.
4. Know who benefits most. In the 2015 Horse & Hound feature, TopSpec names horses with laminitis, PPID, insulin resistance, equine metabolic syndrome or azoturia, and Saracen's nutritionist Lizzie Drury recommends analysis for horses failing to hold condition, losing performance or suffering respiratory disease.
5. Change over gradually. Whatever the results, the BHS advises making feed changes gradually, ideally over 10 to 14 days, to reduce the risk of colic. That includes moving onto a new batch of hay.

In South Africa, lucerne buyers can ask for the National Lucerne Trust grade, and the same core-sampling approach applies to teff, eragrostis and oat hay bought by the load.

Matching Hay to the Horse in Front of You

There is no such thing as the best hay, only the right hay for a particular horse. Start with quantity, because the best analysis in the world is wasted if the amount is guessed.

How Much Hay Should a 500 kg Horse Eat a Day?

The BHS recommends that a horse eats approximately 2 to 2.5 per cent of its bodyweight per 24 hours to meet its daily requirements, and that the daily ration should be no less than 1.5 per cent of bodyweight. That total covers grazing, hay and any bucket feed together. For a 500 kg horse at 2 per cent, the BHS example works out at 10 kg a day. For an overweight horse the BHS suggests reducing the figure towards 1.5 per cent, and not going lower without a vet's instruction.

For overweight horses with insulin dysregulation, the ECEIM consensus gives its own figure: hay at 1.4 to 1.7 per cent of bodyweight as fed (1.25 to 1.5 per cent as dry matter), phased in over one to two weeks. Our equine obesity guide covers that plan in detail. Weigh the hay rather than counting slices or nets, and track the result with regular body condition scoring and a weigh tape.

Choosing Hay by Type of Horse

• Good doers and native ponies: a lower-energy grass hay, analysed for NSC, fed in a quantity that keeps them chewing. Coarser hay or part-replacement with straw (with a balancer) can stretch the eating time without the calories. Our guide to feeding a pony covers the rest of the ration.
• Laminitis-prone, EMS and PPID horses: hay with NSC below the ECEIM's 10 per cent, confirmed by analysis, and not haylage. See our haylage guide for why its lower sugar on paper does not make it the better choice for these horses.
• Horses in hard work: more energy, which a higher-DE hay or some lucerne in the ration can provide, plus free-choice salt because hay supplies so little sodium.
• Youngstock and lactating mares: more protein and calcium. MSD's figure for growing horses is 14 to 16 per cent protein in the total ration, and it advises against unsupplemented warm-season grass hay for these groups.
• Older horses: protein needs may rise, and worn teeth may mean hay is no longer the right forage at all.
• Horses with respiratory disease: hygiene first. Dust-free, mould-free forage, steamed if your vet advises it, matters more than the last percentage point of protein.
• Horses with HYPP: a potassium analysis before you buy.

Hay Versus Grass and Haylage: How the Nutrients Compare

Is hay better for horses than grass? They do different jobs. Fresh grass is far richer in vitamin E, as the Belgian figures show, and grazing lets a horse eat little and often in the way the BHS describes. Hay is what makes a controlled diet possible: you can weigh it, analyse it and choose a batch that suits the horse, which you cannot do with a field.

Haylage sits between the two. The BHS describes it as cut earlier and only partly dried, with typically higher nutritional value than hay but more water, so more of it is needed. Against that, the ECEIM consensus does not recommend haylage for horses with insulin dysregulation, because it produces a bigger insulin response than hay of the same NSC content.

Weigh the hay, read the analysis, use your eyes, nose and hands, and treat cleanliness as seriously as nutrient content. Get those habits right and the nutrients in hay stop being a mystery and start being a tool.

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