Low-Sugar Hay for Horses: What ESC, WSC and NSC Really Mean

By the XES Netting team — bale net-wrap manufacturer · Updated August 20, 2026 · ~13 min read

Somewhere around the second week of hay season, most grass-hay growers get a version of the same phone call. A customer's horse has foundered, or a vet has come back with a blood panel, and now the hay has to be "low sugar." Ask what number they need and about half the time you get silence, and about half the time you get something surprisingly specific.

The forums have been chewing on this for more than a decade, and the discussions follow a predictable arc: eye-rolling about horse owners, a few jokes about selling rained-on hay as "prewashed," and then — usually four or five posts in — somebody who actually farms this market shows up and quietly explains how it works. Those posts are worth reading carefully, because the market is real, it pays a premium, and most of the folk wisdom around it is wrong.

This guide covers what the buyer is really asking for, which lab numbers matter, the one piece of physiology that makes the popular advice unreliable, which levers actually move sugar content, what soaking does, and an honest accounting of whether farming for this market is worth your time.

---

The four letters on a hay test that horse buyers care about

A standard forage test — the one that gives you crude protein, ADF, NDF, TDN and an RFV score — usually will not answer this question at all. As the grower who started one of the longest threads on the subject put it, his basic panel "didn't list a sugar content." You have to order a different package.

Here is what the carbohydrate numbers mean, because the terms get used interchangeably and they are not interchangeable:

That last row is where most of the confusion on both sides of the sale comes from. "NSC" is a calculation, and there are two common ways to run it. WSC + starch is the conservative version. ESC + starch is the version many equine nutritionists now prefer for insulin-dysregulated horses, because it isolates the carbohydrates that are actually absorbed as glucose. The same bale can pass one threshold and fail the other. If a customer says "I need under 10% NSC," the useful follow-up question is which two numbers are you adding?

The number that matters: ESC + starch under 10%

The most consistently useful answer in the whole forum record comes from a Virginia grower who farms this market deliberately. Asked point blank what test to order and what to aim for, he gave the spec in one line:

"You're looking for ESC+Starch to be <10 dry matter basis."

"Our hay is typically low in sugar, potassium and iron - all concerns of special needs horses - it is definitely a niche market worth exploring IMHO."

— VA Haymaker · HayTalk thread 96832

Three things in that answer are worth pulling out. First, ESC + starch, not WSC + starch — the tighter, more physiologically targeted calculation. Second, dry-matter basis, not as-fed; hay at 12% moisture will read differently on the two bases, and the difference is big enough to fail a lot that would otherwise pass. Third, potassium and iron, which almost never come up in these conversations but matter to the same customers, and which a full equine panel reports anyway.

He also flagged the floor, which nobody expects:

"I have also been told that you can drive the sugar content to low (ESC+starch) below 5 and horses don't find it as tasty."

— VA Haymaker · HayTalk thread 94222

So the target is a window, not a race to zero. Under 10 to satisfy the vet; not so far under that the horse walks away from it and the customer blames your hay.

On the buyer's side, when the request is legitimate it usually comes with a paper trail. A Missouri horse owner posting to find a supplier described exactly that:

"Based on the horse's test results, my veterinarian has recommended no more than 10% combined starch (NSC)."

— Marilyn Rogers · HayTalk thread 99005

That is a different customer from the one who read something online. A vet-driven request comes with a threshold, a willingness to pay for testing, and often a willingness to buy a year's supply at once — which is the part that makes this market commercially interesting.

You cannot see sugar, and that is where the argument starts

Here is the tension that runs through every one of these threads. The hay a horse owner pictures when they say "low sugar" and the hay that actually tests low are, in their heads, opposites. One grower's impression of the request:

"I NEED some low sugar hay for my horse it has to be green and fine not to many stems. Not gone to seed no junk."

"even with the test results in there hand they still want the super green rich soft good hay."

— hay king · HayTalk thread 19354

The standard grower response is that low-sugar hay has to be rank, mature, stemmy stuff. A Kentucky grower who is also a horse owner — a useful vantage point — put the conventional version well:

"The best low starch hay (in my experience) is late first cutting hay after the stems have dried. It is often not bright green and pretty, but it is palatable."

— Edd in KY · HayTalk thread 99005

And yet the grower who actually farms the spec says the opposite. When another member put it to him directly — that if colour sells and washed hay loses colour fast, then surely "green hay and low sugar hay cannot be in the same sentence" — his reply in that thread was a flat no: green hay and low sugar do go together, and the real obstacle to green hay is simply leaving it on the ground too many days. His timothy, conditioned with impellers, is a three-day crop, and he reported making some of the greenest, best-testing low-sugar hay of his career that season.

A grower in a different climate described the same effect from the other end — cure it fast enough and you keep the colour:

"timothy is a great horse hay lots of roughage/fiber, long harvest window, and very palateable to horses"

"we did a test this year and were able to get a small batch of timothy hay up cut -baled in 30hrs which is remarkable in our climate"

— ttazzman · HayTalk thread 96832

Both camps are telling the truth. Colour is a record of how long the crop lay in the field and whether it got wet. Sugar is a function of what you planted and how mature it was when you cut it. Those two things are only loosely related, which is why brown hay is often but not always low in sugar, and why green hay is sometimes low too. Colour is a proxy for curing, not for carbohydrate.

The practical consequence: there is no visual inspection, no cutting number, and no rule of thumb that substitutes for a lab result. Anyone selling "low sugar hay" without a test is guessing, and anyone buying it without a test is paying a premium for a guess.

Worth adding, because it corrects a common assumption on the grower side: the buyers are not all asking for garbage. As one grower who had talked to a hay broker in that trade noted:

"From the people I have talked to that are looking for low sugar hay, they aren't looking for sticks but higher protein with less sugar."

— Hayman1 · HayTalk thread 96832

Does cutting at dawn actually make low-sugar hay?

This is the piece of advice that circulates most widely, and it is the one worth understanding properly, because it is half right in a way that leads people astray.

The underlying plant physiology is not in dispute. Grasses and legumes build sugars through photosynthesis all day, faster than they can move them to the roots or burn them, so non-structural carbohydrates climb through the afternoon and peak toward dusk. Overnight, photosynthesis stops, respiration takes over, and the concentration falls until sunrise. So the crop standing in your field genuinely is at its lowest sugar just after dawn.

Growers have observed this directly. A Canadian producer serving a low-sugar customer reported:

"I have a customer who needs low sugar hay. I am not sure of the exact figures but we seem to be able to achieve the desired results by cutting early in the morning before the sun gets on the hay i.e. finish before 7:00 am."

— GOOD HAY · HayTalk thread 90072

And a Texas grower gave the deliberate, contrarian version of the recipe — make the hay badly, on purpose:

"Cut very mature grass hay early in the morning. Do not treat it like prime hay, as that is not your goal."

— hay wilson in TX · HayTalk thread 19354

Why cutting time is a weaker lever than it looks

Cutting does not freeze the number. This is the fact that resolves the whole argument, and it is the one most often left out:

"What good is it going to do to cut at the end of the day if the hay isn't going to do any drying through the night."

"I'm a firm believer in doing whatever it takes to cause the quickest drying. Between that and time of harvest (plant maturity), those are the two most important factors in harvesting quality grass hay."

— Idaho Hay · HayTalk thread 69193

A severed plant behaves like a living thing for a while yet. Hay & Forage Grower puts the mechanism plainly: respiration continues until plant moisture reaches about 50 percent, and for cut material lying in the sun, photosynthesis carries on too. The magazine's conclusion is the line that should govern this entire topic: "Long drying times translate to extended plant respiration following cutting, negating any effect of sugar content at the time of cutting."

Read that carefully. A dawn-cut crop that lies in a wet windrow for three days will keep burning sugar the whole time — which lowers the number, but also bleaches the hay and costs you dry matter and protein. A midday-cut crop that dries in a day locks in more of what it had. The starting value at the moment of cutting is genuinely the smaller term in that equation.

The most telling confirmation comes from the grower who actually sells to this spec and therefore has years of paid lab work to check it against. He does not use the dawn trick at all:

"For grass hay, I haven't found a significant difference between morning and evening cut grass hay on our farm."

— VA Haymaker · HayTalk thread 94222

That is a grower hitting an ESC + starch spec reliably enough to build a customer base on it, telling you the lever everyone reaches for first is the one he could not measure.

Why two extension services appear to contradict each other

This is exactly why growers find conflicting advice and conclude that somebody is wrong. One HayTalk member linked a University of Georgia article and concluded that timing does not matter; another member immediately objected that northern research disagrees, and that the difference is the type of grass.

Go and read the Georgia piece and the objection turns out to be correct. The article says explicitly, in its second paragraph, "For simplicity we are going to talk about bermudagrass" — a warm-season grass — before advising that the best time is to start as soon as dew is off in the morning because "you are not going to lose that much sugar content and you will maximize drying time."

That is sound advice for bermudagrass in Georgia and poor advice to generalise from. Warm-season grasses swing far less across the day than cool-season grasses do, and a humid Southeastern curing environment makes dry-down the dominant risk anyway. In the arid West, where nights are cool and dry-down is fast, the picture flips: cut forage holds what it had, so what it had at cutting matters more. Hay & Forage Grower reaches the same conclusion from the other direction — in the West, "low humidity, cool nights, and plenty of sunshine make for fast dry down rates," so quality is preserved more easily than in the humid East.

The two extension services are not contradicting each other. They are describing different grasses in different drying climates. Neither is a rule you can carry across the country.

The levers that actually move the number, ranked

Putting the research and the field reports together, here is an honest ranking of what you control, strongest first:

1. Species and stand composition. The biggest single lever, and the one you set years before harvest. Legumes push the number up — the Virginia grower's first answer on how he hits his spec was that he has no legumes at all, and that if he had clover, "our sugar numbers would be high." Cool-season grasses run higher than timothy or the warm-season grasses.
2. Maturity at cutting. More mature, more lignin, lower non-structural carbohydrate as a share of the whole. This is also the lever that costs you the most in protein and in customer appeal.
3. Rain and leaching. Highly effective at removing water-soluble sugar and completely uncontrollable, which is why it is a joke on the forums rather than a plan. It takes protein and dry matter with it and can ruin the sale.
4. Drying rate. Slow drying lowers sugar through extended respiration. This works, but you pay for it in colour, leaf and mould risk. It is a lever most growers should refuse to pull deliberately.
5. Time of day at cutting. Real, well-documented, and last on the list — because everything above it, plus your curing weather, can swamp it.

One grower spelled out the deliberate inversion of normal practice that follows from this, which is a useful way to see how far the low-sugar recipe departs from the quality playbook:

"Laying in swathes will help hay dry out faster so less sugar content is lost."

"However to make 'horsey hay' (since apparently horses can't handle high sugar), disregard the swathing and windrow it first thing in the morning before dew is off and plant is at rest."

— BWfarms · HayTalk thread 69193

Note what he is describing: throwing away the wide swath — the single best practice for preserving hay quality — in order to slow drying down. That is a real technique, and it is also a good illustration of why chasing sugar through curing is a bad trade for most operations. You are deliberately making worse hay and hoping the lab rewards you for it.

Is there a low-sugar grass?

Not reliably, and this is the honest answer growers should give. Extension guidance circulated in these threads is blunt about it: there are no "silver bullet" grasses that are consistently low in sugar. Cool-season species such as orchardgrass and fescue can run high; timothy and most warm-season grasses tend to sit in the middle.

What experienced growers in this niche actually do is narrow the field and then test everything anyway. Timothy comes up repeatedly, both because it tends to test lower than orchardgrass or fescue and because horse buyers already want it — see our timothy hay guide for how it behaves agronomically. Teff is the other name that comes up constantly, and it is a genuinely useful option because it also gives you a fast-establishing summer annual you can slot into a rotation.

Two cautions. First, "tends to be lower" is not a spec — the range within a species easily overlaps the range between species. Second, the same grower who recommends timothy will tell you he tests every field separately and lets the customer pick from the results. Species selection narrows the odds; it does not replace the lab.

What soaking does, and what it costs

Most growers meet soaking as the thing the customer does after buying, and it is worth understanding because it changes what you are actually competing with.

"Hay soaking usually takes 30 minutes in warm water or 60 minutes in cold water to lower the carbohydrates."

— Mike120 · HayTalk thread 18590

That summary matches the published work reasonably well. Soaking studies generally report water-soluble carbohydrate reductions in the region of 30–50% after 30 to 60 minutes, with most of the loss happening early and little further benefit from longer soaks. But three findings matter for the sales conversation:

• It is unpredictable. The amount removed varies enormously between hays, even within the same species. Some hays do not drop below a safe threshold at all.
• It strips more than sugar. Potassium losses are large, protein and dry matter also go, and the mineral balance shifts.
• It is a chore. Soaking every feeding, year-round, in freezing weather, is why buyers like the Missouri owner above go looking for hay that tests low in the first place — she said outright she was "trying to avoid hay soaking."

So a tested low-NSC lot is not competing with nothing. It is competing with a bucket of water and thirty minutes of the customer's time — and its selling point is consistency, convenience, and a number on paper.

Is this market worth farming for?

Here the forums are more useful than any marketing article, because the people who tried it say what it cost them.

The cautionary tale first. One grower held a field back all season for a customer who needed hay under 10% sugar, could not find anything poor enough, and lost his window:

"Thats good to know, but I have sense fired that hay customer! That stupid ploy set me back 3 weeks of perfect second cut weather!"

— skyrydr2 · HayTalk thread 90072

That is the failure mode: letting one customer's spec dictate your harvest schedule. Three weeks of good weather is worth more than almost any single hay order.

And then the verdict from the grower who did it properly, for years, with the testing and the segregation and the customer education — which is the most valuable paragraph in the entire forum record on this subject:

"Oddly enough, but no surprise, most of our hay customers could care less about test results or the verity of hay."

"All of the above takes a lot of time, expense and face/information time with the field and customer. In total, I'm not sure it's worth it."

— VA Haymaker · HayTalk thread 94222

That is not a reason to avoid the market. It is a reason to size it correctly. The realistic read from the threads: something like one in ten horse-hay enquiries mentions sugar, most of those callers will not pay for testing, and the minority who will are genuinely loyal, buy in volume, and travel a long way to a reliable supplier. It is a segment of your existing horse trade, not a business model on its own.

A working protocol if you decide to sell into it

If you want the premium without wrecking your season, the forum consensus and the lab guidance converge on roughly this:

1. Do not change your harvest schedule. Cut everything on quality timing. You will find low-testing lots among what you already make far more often than you expect.
2. Define the lot before you test it. One field, one cutting, one stack. Mixing lots after the fact makes the test meaningless — the same discipline we cover in how to sell hay.
3. Core-sample properly and order the right panel. Ask for a wet-chemistry equine package that reports WSC, ESC, starch and minerals. Equi-Analytical's Trainer 603 is the panel named repeatedly by growers in this trade. NIR is cheaper but less reliable for sugar fractions.
4. Report both calculations. Publish WSC + starch and ESC + starch, both dry-matter basis. It costs nothing and pre-empts the most common misunderstanding.
5. Segregate and label physically. A tested lot is only worth a premium while you can still prove which bales it is.
6. Let the buyer test before committing. The Kentucky grower's advice to buyers — buy three or four bales, sample immediately, rush the test while that stack is still intact — is equally good advice for the seller, because it turns a dispute into a data point.
7. Never promise a number in advance. Promise a test. Weather, stand and maturity will do what they do.

That last discipline is exactly how the growers who succeed here describe their own operation:

"We do a separate test for each field and segregate it for the customer to choose based on test results."

— VA Haymaker · HayTalk thread 94222

Note the direction of that sentence. He does not grow low-sugar hay to order; he tests what he grew and lets the customer pick the lot that fits. That inversion is the whole trick.

For the mechanics of core sampling and reading the rest of the report, see how to read a hay test.

Where XES fits

We make bale net wrap, so take this in the spirit it is offered: net wrap is not going to change a carbohydrate number. Nothing on the outside of a bale can.

What the package does affect is whether the bale you deliver still resembles the lot you tested. That is a real problem in this niche and an under-discussed one. Once you have paid for a wet-chemistry panel and sold on the strength of it, weathering on the outside of a round bale quietly moves you away from the analysis on the paperwork — rain leaches sugar, yes, but it also leaches protein and minerals, spoils the outer shell, and creates the dust and mould that the same customers care intensely about, since metabolic horses are frequently also managed for airway disease.

Three practical points:

• Shed water, keep the test honest. A tight, fully wrapped bale sheds rain far better than a twine-tied one, so less of your tested lot turns into spoilage. We covered the mechanism in does net wrap breathe and shed water, and the storage side in net-wrapped bale storage outside.
• Wrap colour as a lot marker. If you are running segregated lots, a distinct wrap colour on the tested stack is a cheap, visible way to keep them from getting mixed on a busy loading day.
• Be honest about format. Most low-NSC hay still moves as small squares, and net wrap is a round-baler product. If you sell round bales into horse barns, the separate safety questions around binding removal are covered in is net-wrapped hay safe for horses.

What we are deliberately not claiming

Several things get asserted confidently in these discussions that we will not repeat, because we could not verify them to a standard we would want a customer to rely on:

• A specific percentage drop from cutting at dawn. Figures circulate, including a widely repeated claim of several points between sunrise and mid-afternoon. The direction is well established; a number you could plan a harvest around is not, and it would vary by species, region and season anyway.
• That any named variety is reliably "low sugar." We found no variety-level data robust enough to put a grower's reputation behind.
• Any veterinary threshold beyond the widely cited 10% guideline. We are a net wrap manufacturer. Feeding decisions for a laminitic, insulin-resistant or PPID horse belong to that horse's vet, working from that horse's bloodwork and that specific lot's analysis.
• A price premium figure. Growers describe the segment as worth exploring but do not publish numbers, and premiums vary far too much by region to quote.

---

Frequently asked questions

What is a safe sugar level in hay for a horse with laminitis or insulin resistance?

The commonly cited guideline is a combined ESC + starch under 10% on a dry-matter basis, with some programs allowing up to 12%. That calculation isolates the carbohydrates absorbed as glucose, so it targets the insulin response directly. The threshold for any individual horse is a veterinary decision based on that horse's bloodwork, not a marketing claim.

What is the difference between WSC, ESC and NSC on a hay test?

WSC is water-soluble carbohydrate — simple sugars plus fructans. ESC is ethanol-soluble carbohydrate, capturing only the simple sugars, and is always the smaller number. NSC is calculated rather than measured, conventionally as WSC + starch, though ESC + starch is often preferred for metabolic horses. Always ask which formula produced a quoted NSC figure.

Does cutting hay early in the morning lower its sugar content?

Standing forage genuinely is lowest just after dawn and peaks toward dusk, but cutting does not lock the value in. Respiration continues in the cut crop until moisture falls to roughly 50%, so drying rate can matter more than the hour you mowed. Treat it as a real but weak lever compared with species and maturity.

Can green, leafy hay still be low in sugar?

Yes. Colour records curing history — days on the ground and whether it got wet — far more than carbohydrate content. Growers in this market report making bright green hay that tests low by using fast-drying grass species and short cure times. You cannot judge sugar by looking at a bale.

How much sugar does soaking hay remove?

Trials generally report water-soluble carbohydrate reductions of roughly 30–50% after 30 to 60 minutes, with most of the loss happening early. Results vary widely between hays, and soaking also removes substantial potassium plus some protein and dry matter. Effective, but not precise.

Which grass species makes the lowest sugar hay?

None reliably. Cool-season grasses such as orchardgrass and fescue can run high; timothy and most warm-season grasses tend to be moderate. Timothy and teff are the species most often named by growers serving this market, but the within-species range overlaps the between-species range, so every lot still needs a test.

---

The bottom line

Low sugar hay is a real, testable, premium product and one of the few horse-hay niches where a number on paper actually closes a sale. The number is ESC + starch under 10% on a dry-matter basis, it is invisible to the eye, and it is set mostly by what you planted and how mature it was when you mowed — not by the clock.

The advice to cut at dawn is not wrong, it is just small. A cut plant keeps burning its own sugar until the windrow dries below about 50% moisture, which is why Georgia tells bermudagrass growers not to bother and northern growers of cool-season grass find that it matters. Before you take either side, check which grass and which climate the advice was written for.

The commercially sensible approach is the least romantic one: do not rearrange your season around it. Cut on quality timing, keep lots clean and separate, test the ones your customers ask about, publish both NSC calculations, and let the lab find your low-sugar hay for you. You will get the premium without the three lost weeks of good weather.

Forum quotes are reproduced verbatim with attribution and linked to their source threads; follow the links to read the originals. Nothing here is veterinary advice — feeding decisions for a laminitic, insulin-resistant or PPID horse should be made with that horse's veterinarian, using a current analysis of the specific lot being fed.

Featured photo: Horse eating hay in winter by Minoo, licensed under CC BY-SA 4.0, via Wikimedia Commons.

---