Feed Your Steed - Equine Diets Based on Science
- Qualified Independent Equine Nutritional Advice Horses are more than just performers, they are family.
Equine Nutrition is predominately a biological science, & as such, influences the entire horse’s body & cognizance. When helping horse-owners, I try to take exceptional care to achieve a thorough understanding of all the aspects of your horse's unique lifestyle, whether it is a competition horse or a retiree. This holistic approach permits me to analyse each horse's specific & individual situation
. Horses are special & the bonds we form with them are like no other. For all their large size, they are really quite delicate & do rely on us to keep them healthy. Feeding horses appropriately for their age, body condition, physical requirements, & even their emotional temperament, requires more than hug & a smile ……. Horse’s, like people, are individuals & should be fed as such. What applies for a particular horse, may not work for another. This is why it is baffling to buy a supplement, let's say, based on the promoted benefits alone. Or, feeding the new wonder horse supplement on the market as your friend does to their horse. This may not work for your horse. This is where comprehensive nutritional advice from a qualified equine nutrition professional is advantageous. The advice you receive should be designed for your horse & no one else's. So, if you find you need friendly, practical advice & information in maximising & maintaining your horse's health through dietary means consider obtaining qualified equine nutritional support from Feed Your Steed, to help you make sense of it all.
It’s the little things ❤️
Just been to collect some Curulli Meadow hay for the horses and was very kindly handed a lovely fresh, warm scone with strawberry jam and cream by Paul 🥰🍓
Absolutely made my afternoon — I was so chuffed! There are some genuinely lovely people in the horse and hay world. Thank you so much for the unexpected treat… it definitely didn’t last long! 😂☕️
𝐄𝐗𝐓𝐑𝐔𝐃𝐄𝐃 𝐃𝐎𝐄𝐒 𝐍𝐎𝐓 𝐀𝐔𝐓𝐎𝐌𝐀𝐓𝐈𝐂𝐀𝐋𝐋𝐘 𝐌𝐄𝐀𝐍 𝐁𝐄𝐓𝐓𝐄𝐑
Sometimes a new feed or supplement comes onto the market, and you immediately think:
“Yes! That is going to be incredibly useful for this horse, that client and their feeding management.”
Then there are other products that make you stop and ask:
Why? 🤔
Extruded sugar beet pulp is one of those products for me.
The same question can apply to extruded lupins and, in many situations, extruded oats.
This does not mean extrusion is bad or that extruded feeds never have a place.
Extrusion is a valuable feed-processing tool — but ideally it should solve a genuine nutritional or management problem, rather than simply making an ingredient sound more advanced.
🤔 𝐅𝐈𝐑𝐒𝐓 — 𝐖𝐇𝐀𝐓 𝐃𝐎𝐄𝐒 “𝐏𝐑𝐎𝐂𝐄𝐒𝐒𝐄𝐃” 𝐀𝐂𝐓𝐔𝐀𝐋𝐋𝐘 𝐌𝐄𝐀𝐍?
The word processed can sometimes cause confusion.
People hear “processed horse feed” and compare it with highly processed human foods containing multiple refined ingredients, flavourings, preservatives, emulsifiers and other additives.
But in equine nutrition, processing may simply mean rolling, crushing, flaking, micronising, steam cooking or extrusion.
These processes may be used to improve chewing, increase accessibility of starch to digestive enzymes, make a product easier to prepare or help a horse with compromised teeth.
So:
Processed does not automatically mean unhealthy.
But equally:
More processing does not automatically mean nutritionally superior.
Rather than becoming caught up in whether something is “processed”, the better question is:
What is the processing actually achieving, and is there a genuine reason for it?
⚙️ 𝐖𝐇𝐀𝐓 𝐃𝐎𝐄𝐒 𝐄𝐗𝐓𝐑𝐔𝐒𝐈𝐎𝐍 𝐃𝐎?
Extrusion uses heat, moisture and pressure to change the physical structure of a feed.
One of its most useful nutritional effects is starch gelatinisation, which can make starch more accessible to digestive enzymes in the horse’s small intestine.
This is particularly useful for cereal grains such as:
• barley
• maize/corn
• wheat
The botanical source of starch matters.
Starch from different grains is not digested equally, and the amount digested before reaching the caecum varies according to both the grain and the way it has been processed.
Thermal and hydrothermal processing can substantially improve precaecal starch digestion, particularly with harder-to-digest grains such as barley and maize (de Fombelle et al., 2004; Julliand et al., 2006; Thorringer et al., 2020).
That is a genuine nutritional reason for processing.
🌾 𝐖𝐇𝐘 𝐃𝐎𝐄𝐒 𝐒𝐓𝐀𝐑𝐂𝐇 𝐃𝐈𝐆𝐄𝐒𝐓𝐈𝐎𝐍 𝐌𝐀𝐓𝐓𝐄𝐑?
The horse does not have an unlimited capacity to digest starch in the small intestine.
When too much starch is fed in one meal, or when starch is poorly accessible to digestive enzymes, more may escape small-intestinal digestion and enter the hindgut.
There it is rapidly fermented by starch-utilising bacteria, which can:
• increase organic-acid production
• reduce hindgut pH
• alter microbial populations
• disrupt fibre-digesting bacteria
• contribute to hindgut acidification and, when sufficiently severe, hindgut acidosis
The response also differs according to the starch source (Destrez et al., 2015; Harlow et al., 2015).
High-starch, low-fibre diets have been associated with disruption of the hindgut microbiome and behavioural responses consistent with dietary stress and possible intestinal discomfort (Destrez et al., 2015).
Starch intake also matters to the stomach.
In an observational study of 201 horses, feeding more than 1 g starch/kg body weight per meal, or more than 2 g/kg body weight across the day, was associated with an increased risk of clinically significant gastric ulceration (Luthersson et al., 2009).
For a 500 kg horse this equates to:
• 500 g starch in one meal
• 1,000 g starch across the day
These are practical risk-management boundaries — not exact physiological cliff edges.
And remember:
Extrusion may improve starch digestibility, but it does not remove the starch from the feed. An extruded high-starch feed can still supply too much starch if the serving size is excessive.
🥣 𝐋𝐄𝐓’𝐒 𝐔𝐒𝐄 𝐎𝐀𝐓𝐒 𝐀𝐒 𝐀𝐍 𝐄𝐗𝐀𝐌𝐏𝐋𝐄
Oats contain substantial starch, but oat starch is generally more accessible to the horse’s digestive enzymes than starch from barley or maize.
Research reviews suggest that simple processing such as rolling or crushing oats may provide relatively little additional improvement in precaecal starch digestion compared with the much larger benefit thermal processing can provide for grains such as maize (Julliand et al., 2006).
Suppose the oats being fed contain approximately 40% starch as-fed.
Then:
• 1 kg oats supplies approximately 400 g starch
• 500 g oats supplies approximately 200 g starch
For a 500 kg horse, the previously discussed starch boundaries would equate to approximately:
• 1.25 kg of these oats in one feed
• 2.5 kg across the whole day
If divided into three feeds, the daily amount would be approximately 830 g per feed.
But these are examples, not recommended feeding rates.
The actual amount must be calculated from the starch percentage of the oats or complete feed being used.
Many horses need considerably less, particularly those with insulin dysregulation, previous laminitis, gastric disease, low energy requirements or limited workloads.
Whole oats can therefore be perfectly appropriate for some horses with good teeth when the horse genuinely requires the energy, the starch load has been calculated, adequate forage is supplied, and the overall ration is balanced.
Rolled or flaked oats may be useful for horses with compromised teeth.
But extrusion should not automatically be considered necessary for every horse eating oats — nor does extrusion make an unsuitable high-starch ration automatically safe.
🌱 𝐒𝐎 𝐖𝐇𝐘 𝐄𝐗𝐓𝐑𝐔𝐃𝐄 𝐒𝐔𝐆𝐀𝐑 𝐁𝐄𝐄𝐓 𝐏𝐔𝐋𝐏?
Despite its name, sugar beet pulp is not the whole sugar beet.
It is the fibrous material remaining after most of the sugar has been extracted.
Some products may have molasses added back, so the analysis of the finished product should always be checked.
Sugar beet pulp itself is not a high-starch cereal grain.
It is primarily a highly fermentable, pectin-rich fibre source.
Research has successfully used beet pulp to replace part of the barley in equine diets, increasing fermentable fibre and reducing dietary starch while maintaining good nutrient utilisation (Jensen et al., 2014).
Beet pulp does not require extrusion for the same starch-related reason that maize or barley may benefit from thermal processing.
A recent equine study comparing different physical forms of sugar beet pulp found that processing affected hydration characteristics and feeding behaviour, but the nutritional value remained similar (Grimm et al., 2025).
Of course, an extruded product may still:
• rehydrate more quickly
• provide a consistent texture
• be easier for horses with poor teeth
• reduce sorting or dust
• save preparation time
Those are perfectly valid management benefits.
But management convenience and nutritional superiority are not necessarily the same thing.
And this is where I struggle to do backflips & handstands over every new feed that comes onto the market.
If an existing beet-pulp already:
• provides an excellent fermentable fibre source
• is low in starch
• softens and rehydrates quickly
• is readily accepted
• and costs considerably less
…then I have to ask:
What genuine nutritional problem is the more expensive extruded version solving?
If it saves an owner five or ten minutes and that convenience matters to them, fantastic.
But it does not automatically make the product nutritionally better.
Sometimes the original product was already a very good idea.
🌿 𝐖𝐇𝐀𝐓 𝐀𝐁𝐎𝐔𝐓 𝐄𝐗𝐓𝐑𝐔𝐃𝐄𝐃 𝐋𝐔𝐏𝐈𝐍𝐒?
This discussion refers specifically to suitable feed-grade sweet lupins.
Feed-grade sweet lupins are generally high in protein and fibre, contain useful levels of fat and have very little starch.
In one analysed narrow-leafed lupin sample, starch accounted for only approximately 0.2%, although actual composition varies with species, variety and growing conditions (Arzami et al., 2022).
Much of the carbohydrate in lupins consists of non-starch polysaccharides and oligosaccharides rather than cereal starch (van Barneveld, 1999).
So extrusion of lupins cannot automatically be justified on the basis that a large starch load needs to be gelatinised to protect the horse’s hindgut.
Processing may make lupins easier to prepare, more consistent or easier for horses with poor teeth. But rolled, crushed, flaked lupins may also be perfectly suitable and considerably less expensive.
❓ 𝐃𝐎 𝐖𝐄 𝐍𝐄𝐄𝐃 𝐓𝐎 𝐉𝐔𝐌𝐏 𝐎𝐍 𝐄𝐕𝐄𝐑𝐘 𝐍𝐄𝐖 𝐅𝐄𝐄𝐃 𝐁𝐀𝐍𝐃𝐖𝐀𝐆𝐎𝐍?
No.
Some new feeds are genuinely exciting because they solve a problem.
Perhaps they:
• improve digestibility
• lower starch
• help a difficult-to-feed horse
• make feeding safer
• provide a nutrient that was previously difficult to supply
• or make a difficult management situation substantially easier
Those are innovations worth getting excited about.
But I cannot jump on every new-feed bandwagon simply because an ingredient has been put through another manufacturing process.
Sometimes I look at a new product and think: The original ingredient was already doing a perfectly good job.
A new version may be faster, tidier or more convenient.
Convenience certainly has value.
But convenience and nutritional superiority are not the same thing.
💰 𝐁𝐄𝐅𝐎𝐑𝐄 𝐏𝐀𝐘𝐈𝐍𝐆 𝐌𝐎𝐑𝐄 — 𝐀𝐒𝐊 𝐖𝐇𝐘
Before paying more, ask:
• What nutritional problem is the processing solving?
• Is this ingredient naturally high in starch?
• Does processing meaningfully improve its digestion?
• Does my horse have a specific reason for needing this form?
• What are the starch and sugar percentages?
• Are the figures as-fed or dry matter?
• What is the recommended daily amount?
• What is the actual cost per day?
• How does it compare with the simpler alternative?
And compare products properly.
A nutrient value reported on a dry-matter basis cannot be directly compared with another feed reported as-fed without conversion.
Likewise, price per bag is not the same as cost per day.
For quick-soak sugar beet flakes, lupin products or similar feeds that soften rapidly in cold or warm water, spending a few minutes preparing them may leave considerably more money available for the forage, quality protein, vitamins, minerals and other nutrients the horse genuinely needs.
Always follow the manufacturer’s preparation and soaking instructions.
𝐓𝐇𝐄 𝐓𝐀𝐊𝐄-𝐇𝐎𝐌𝐄 𝐌𝐄𝐒𝐒𝐀𝐆𝐄
❌ New does not automatically mean better.
❌ Processed does not automatically mean unhealthy.
❌ Extruded does not automatically mean safer.
❌ More expensive does not automatically mean more nutritious.
Sometimes extrusion is exactly the processing method a feed needs.
At other times, it mainly provides convenience or a different physical form.
A feed company being able to extrude an ingredient is not the same thing as your horse needing that ingredient extruded.
✅ I am not anti-processing.
✅ I am not anti-innovation.
✅ I am pro-purpose.
🤔 Show me what the processing achieves for this ingredient and this horse.
If it solves a genuine nutritional or management problem — fantastic.
If it does not, sometimes the tried-and-tested option remains an excellent feed.
💙 If you found this post useful, please consider giving it a Like, leaving a comment or sharing it with other horse owners.
These educational posts take a considerable amount of time to research, fact-check and reference properly, and your likes and shares help them reach more horse owners who may also benefit from the information.
And as always, if a post gets you thinking, questioning or looking more closely at what is actually in your horse’s feed, then it has done its job. 😊🐴
Thank you for supporting Feed Your Steed and evidence-based equine nutrition.
📚 𝐑𝐄𝐅𝐄𝐑𝐄𝐍𝐂𝐄𝐒
Arzami, A., Morais de Carvalho, D., Vilaplana, F., Stoddard, F., & Mikkonen, K. S. (2022). Narrow-leafed lupin (Lupinus angustifolius L.): Characterization of emulsification and fibre properties. Future Foods, 6, 100192. https://doi.org/10.1016/j.fufo.2022.100192
de Fombelle, A., Veiga, L., Drogoul, C., & Julliand, V. (2004). Effect of diet composition and feeding pattern on the prececal digestibility of starches from diverse botanical origins measured with the mobile nylon bag technique in horses. Journal of Animal Science, 82(12), 3625–3634. https://doi.org/10.2527/2004.82123625x
Destrez, A., Grimm, P., Cézilly, F., & Julliand, V. (2015). Changes of the hindgut microbiota due to a high-starch diet can be associated with behavioral stress response in horses. Physiology & Behavior, 149, 159–164. https://doi.org/10.1016/j.physbeh.2015.05.039
Grimm, P., Terra Braga, M., Coulmier, D., Julliand, V., Destrez, A., & Julliand, S. (2025). Processing and soaking of sugar beet pulp changes the feeding behavior of horses. Animal Feed Science and Technology, 327, 116426. https://doi.org/10.1016/j.anifeedsci.2025.116426
Harlow, B. E., Donley, T. M., Lawrence, L. M., & Flythe, M. D. (2015). Effect of starch source (corn, oats or wheat) and concentration on fermentation by equine faecal microbiota in vitro. Journal of Applied Microbiology, 119(5), 1234–1244. https://doi.org/10.1111/jam.12927
Jensen, R. B., Austbø, D., Bach Knudsen, K. E., & Tauson, A.-H. (2014). The effect of dietary carbohydrate composition on apparent total tract digestibility, feed mean retention time, nitrogen and water balance in horses. Animal, 8(11), 1788–1796. https://doi.org/10.1017/S175173111400175X
Julliand, V., de Fombelle, A., & Varloud, M. (2006). Starch digestion in horses: The impact of feed processing. Livestock Science, 100(1), 44–52. https://doi.org/10.1016/j.livprodsci.2005.11.001
Luthersson, N., Nielsen, K. H., Harris, P., & Parkin, T. D. H. (2009). Risk factors associated with equine gastric ulceration syndrome (EGUS) in 201 horses in Denmark. Equine Veterinary Journal, 41(7), 625–630. https://doi.org/10.2746/042516409X441929
Thorringer, N. W., Weisberg, M. R., & Jensen, R. B. (2020). The effects of processing barley and maize on metabolic and digestive responses in horses. Journal of Animal Science, 98(12), skaa353. https://doi.org/10.1093/jas/skaa353
van Barneveld, R. J. (1999). Understanding the nutritional chemistry of lupin (Lupinus spp.) seed to improve livestock production efficiency. Nutrition Research Reviews, 12(2), 203–230. https://doi.org/10.1079/095442299108728938
Image created using AI for illustration. Nutrition information written and reviewed by Feed Your Steed.
SUPER FIBRES, SCFAs & METABOLIC HORSES
Why one fermentation product does not tell the whole story
Image created using AI for illustration. Nutritional information was written by Feed Your Steed.
Sorry it has taken a while to write this post. I was never a fast writer when writing any assignment or thesis. I still draft out work with pen and paper first before writing it up. Old habits die hard, or am I showing my age?
Following a recent discussion regarding highly fermentable “super fibres”, short-chain fatty acids (SCFAs/VFAs), glucose production and their suitability for horses with insulin dysregulation, I wanted to look more closely at what the cited research actually demonstrates.
This is not about dismissing propionate, acetate, butyrate or the energy supplied through hindgut fermentation. They are important components of normal equine physiology.
The question is whether we can take an average SCFA ratio, apply it equally to very different fibre ingredients, and then conclude that highly fermentable fibres such as beet pulp, soybean hulls or lupin hulls are inherently unsuitable for metabolic horses.
When the individual studies are examined, the answer is considerably more nuanced.
KEY POINT: SCFAs matter, but one average propionate figure cannot define the metabolic suitability of every highly fermentable fibre. Different fibre sources produce different fermentation profiles, and for metabolic horses we still need to consider the whole diet, including sugar, starch, meal size, total energy intake and the individual horse’s insulin response.
What we agree on
Highly fermentable fibres are not calorie-free.
Different fibre sources are not necessarily metabolically identical.
A feed being low in sugar and starch does not mean it can be fed in unlimited quantities.
Total energy intake remains extremely important, particularly when an overweight horse needs to lose weight.
Acetate, propionate and butyrate all contribute to equine energy metabolism.
Where we differ is in what the production of these SCFAs actually proves regarding the safety or otherwise of individual fibre ingredients for horses with equine metabolic syndrome (EMS) or insulin dysregulation (ID).
The production of acetate, propionate and butyrate during normal hindgut fermentation does not, by itself, establish that beet pulp, soybean hulls, lupin hulls or other highly fermentable fibres are inherently unsafe for horses with ID or EMS.
________________________________________
Propionate is gluconeogenic, but that does not make it equivalent to feeding a bolus of glucose
Propionate absorbed from the hindgut is transported through the portal circulation to the liver.
Within hepatic cells, it undergoes several metabolic steps:
Propionate → propionyl-CoA → methylmalonyl-CoA → succinyl-CoA
Succinyl-CoA enters the tricarboxylic acid (TCA) cycle. Carbon derived from propionate can subsequently contribute to oxaloacetate and hepatic gluconeogenesis.
Propionate is therefore correctly described as a gluconeogenic substrate.
However, it would be misleading to equate regulated hepatic gluconeogenesis from propionate with the rapid intestinal absorption of glucose arising from a high-sugar or readily digestible starch meal.
Glucose produced endogenously can be oxidised by tissues, stored as glycogen or released into the circulation according to metabolic demand.
Gluconeogenesis is part of normal glucose homeostasis rather than an uncontrolled conversion of propionate into a sudden glucose load (Bergman, 1990).
________________________________________
What did Simmons and Ford actually demonstrate?
Simmons and Ford (1991) studied only two ponies receiving hay or hay plus wheat bran.
They reported mean total glucose-production rates of approximately:
• 120 mg/kg bodyweight/hour on hay; and
• 92 mg/kg bodyweight/hour on hay plus wheat bran.
They estimated that approximately:
• 50% of total glucose production in the hay-fed ponies; and
• 61% in the hay-and-bran-fed ponies
was derived from propionate produced in the colon (Simmons & Ford, 1991).
This distinction is extremely important.
The paper reported:
Approximately 50–61% of total glucose production was derived from colonic propionate.
It did not report:
Approximately 50–61% of all propionate produced was converted to glucose.
The denominator has changed between those two statements.
They are mathematically and physiologically different.
It would therefore also be incorrect to take an estimated energetic value for daily propionate production and simply divide it by two to calculate how much propionate energy becomes glucose.
________________________________________
Where does a figure of approximately 500 g glucose come from?
The Simmons and Ford data can be used to illustrate how a figure approaching 500 g/day might be calculated.
Using an illustrative 350-kg pony receiving hay:
120 mg/kg/hour × 350 kg × 24 hours × 50% = approximately 504 g glucose/day derived from propionate
Likewise, using an illustrative 370-kg pony receiving hay plus bran:
92 mg/kg/hour × 370 kg × 24 hours × 61% = approximately 498 g/day
These calculations help explain where a figure close to 500 g might originate.
However, this represents estimated glucose production and turnover integrated across 24 hours.
It does not mean that 500 g of glucose was simultaneously present in the horse’s bloodstream.
Nor does it mean that the horse received the physiological equivalent of eating a 500-g glucose meal.
Simmons and Ford measured glucose production and entry using tracer methodology. Glucose was continually being produced, utilised, stored and recycled.
An earlier study by Ford and Simmons (1985), again involving only two ponies, estimated that approximately 7% of total glucose production originated from caecal propionate.
The considerable difference between caecal and colonic estimates itself demonstrates why digestive location, methodology, diet and individual variation matter.
Neither study involved horses diagnosed with EMS.
Neither investigated postprandial insulin responses or laminitis.
Neither compared beet pulp, soybean hulls and lupin hulls as individual fibre ingredients (Ford & Simmons, 1985; Simmons & Ford, 1991).
________________________________________
Butyrate also matters
Propionate is not the only SCFA produced through hindgut fermentation.
Butyrate is an important fermentation product and should not be overlooked when comparing fibre sources.
Butyrate is extensively utilised by intestinal epithelial cells as an energy source and contributes to epithelial metabolism and normal gastrointestinal function.
Its proportion also varies according to fibre substrate, feeding rate, microbial community and other components of the ration.
This provides another reason why highly fermentable fibres should not all be grouped under one assumed SCFA profile.
A fibre source producing proportionally more acetate and butyrate and less propionate is not metabolically identical to one producing a greater proportion of propionate.
The complete fermentation profile matters, not one SCFA considered in isolation.
________________________________________
There is no universal “super-fibre SCFA ratio”
Different fibre substrates do not necessarily produce identical proportions of acetate, propionate and butyrate.
The proportions can change according to:
• fibre source;
• inclusion rate;
• accompanying diet;
• adaptation of the microbial population;
• sampling location;
• sampling time; and
• the individual horse.
This is demonstrated particularly well when beet pulp and soybean-hull research are compared.
Beet pulp
Moore-Colyer et al. (2000) studied caecally fistulated ponies receiving several fibre-based diets.
A 50:50 diet of unmolassed sugar beet pulp and hay cubes produced an approximate molar profile of:
Acetate ≈ 80%
Propionate ≈ 15%
Butyrate ≈ 5%
These figures should not be described as “the SCFA ratio of beet pulp”.
They describe the fermentation profile measured from that particular beet-pulp-and-hay diet under those experimental conditions.
Nevertheless, they clearly demonstrate why applying one generic SCFA ratio to every highly fermentable fibre is problematic (Moore-Colyer et al., 2000).
________________________________________
Soybean hulls show how inclusion rate can alter SCFA proportions
Coverdale et al. (2004) studied four healthy caecally cannulated Quarter Horse geldings receiving diets in which soybean hulls replaced 0%, 25%, 50% or 75% of hay.
The molar proportion of propionate was:
0% soybean hulls — 15.7%
25% — 18.0%
50% — 16.6%
75% — 21.9%
The acetate: propionate ratio changed from approximately 4.9 to 3.3 at the highest soybean-hull inclusion.
Butyrate declined from approximately 5.3% to 3.9%, while total caecal VFA concentration increased from approximately 70 to 109 mM (Coverdale et al., 2004).
This demonstrates two important points.
First, fibre substrate and inclusion rate can alter SCFA proportions.
Second, the highest propionate proportion — 21.9% — occurred when soybean hulls replaced a very large 75% of the hay.
That result should therefore not be taken as a blanket statement that soybean hulls always produce 21.9% propionate.
Kabe et al. (2016) subsequently evaluated soybean hulls at more moderate inclusion rates within equine concentrates and did not demonstrate significant alterations in measured faecal SCFA proportions or adverse effects on the digestive parameters assessed.
This again demonstrates why results obtained at extreme forage-replacement rates should not automatically be extrapolated to substantially smaller ingredient inclusions in commercial feeds.
________________________________________
More recent beet-pulp research is also nuanced.
More recent equine research has not established one new universal acetate:propionate:butyrate ratio for beet pulp.
Jensen et al. (2016) compared hay, hay plus molassed sugar beet pulp, hay plus barley, and hay plus barley plus molassed sugar beet pulp in caecally cannulated horses.
The hay and hay-plus-beet-pulp treatments showed relatively stable metabolic responses compared with the barley-containing diets.
Brøkner et al. (2016) likewise demonstrated that dietary carbohydrate composition alters both hindgut fermentation and systemic metabolic responses.
These studies reinforce an important distinction:
Detecting propionate in the hindgut does not, by itself, demonstrate that a feed produces an excessive postprandial glucose or insulin response.
________________________________________
Molassed and unmolassed beet pulp should not automatically be treated as identical.
Hansen et al. (2020) compared orchard-grass hay with diets containing molassed sugar beet pulp, almond hulls or steam-crimped oats.
The molassed beet-pulp treatment produced measurable postprandial glucose and insulin responses while also increasing fermentation products.
This should not be interpreted as meaning that every beet-pulp product produces an identical response.
A product containing substantial added molasses and an unmolassed low-sugar beet pulp may provide very different amounts of readily available carbohydrate per meal.
Therefore, analysis of the actual product remains important.
We should know:
ESC/simple sugars
Starch
WSC where relevant
Feeding rate
The actual grams consumed per meal
Rather than relying only on the ingredient name.
________________________________________
Lupin hulls should not simply inherit another fibre’s SCFA profile
Direct peer-reviewed equine research specifically quantifying acetate, propionate and butyrate production from lupin hulls, particularly in insulin-dysregulated horses, remains limited.
This limitation should be openly acknowledged.
We therefore should not assign lupin hulls the beet-pulp SCFA profile.
Nor should we assign them the soybean-hull profile.
Nor should we automatically assign a generic whole-hindgut SCFA ratio.
A lack of direct research is not proof of safety.
But equally, a lack of direct research is not proof of harm.
Laboratory analyses (wet chemistry) of lupin-hulls products can demonstrate low starch and sugar concentrations, and those analysed values are relevant when formulating diets for insulin-dysregulated horses.
Suitability still needs to be considered according to:
• Analysis of the actual product;
• ESC/simple sugars;
• WSC where available;
• Starch;
• feeding rate;
• grams of sugar and starch delivered per meal;
• total digestible energy;
• total ration composition;
• body condition;
• exercise; and
• the individual horse’s insulin response.
________________________________________
What about WSC, ESC and fructans?
These terms also need to be interpreted correctly.
ESC broadly represents simple sugars extracted under the laboratory method used, predominantly glucose, fructose and sucrose.
WSC includes these simple sugars plus water-soluble fructan fractions.
Fructans are not digested enzymatically in the small intestine to the same extent as glucose, fructose, sucrose or readily digestible starch.
They largely proceed to the hindgut where they undergo microbial fermentation.
That means WSC, ESC and starch do not all represent identical metabolic pathways.
For an insulin-dysregulated horse, we therefore need to consider not only a single “NSC percentage”, but what actually makes up that carbohydrate fraction and how much of each component is consumed.
________________________________________
SCFAs should not be ignored, but neither should dietary sugar and starch
None of this suggests that SCFAs should be disregarded when formulating diets for metabolic horses.
They absolutely matter.
The issue is whether one SCFA should be considered in isolation while the rest of the diet is overlooked.
Dietary simple sugars and enzymatically digestible starch can be absorbed from the small intestine and contribute directly to postprandial glucose and insulin responses.
Fermentable fibre follows another route.
It undergoes microbial fermentation predominantly in the hindgut, after which SCFAs are absorbed and metabolised.
Both pathways provide energy.
They are not physiologically interchangeable.
Therefore, when evaluating a supplementary feed for an insulin-dysregulated horse, we need to ask:
• What are its analysed ESC/sugar concentrations?
• What is its starch concentration?
• What is its WSC where relevant?
• How many grams of sugar and starch are actually supplied in each meal?
• What quantity of feed is being fed?
• What is the horse’s total energy intake?
• What forage and pasture are being consumed?
• Is the horse overweight, lean or in appropriate body condition?
• Is weight loss required?
• Is the horse exercising?
• What is the horse’s individual insulin response?
• Is the supplementary feed replacing another energy source or simply being added to an already adequate ration?
Those questions cannot be replaced by looking at propionate alone.
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Insulin response remains central to hyperinsulinaemia-associated laminitis
Prolonged experimentally induced hyperinsulinaemia has produced laminitis, and insulin dysregulation is central to hyperinsulinaemia-associated laminitis (de Laat et al., 2010; Durham et al., 2019).
Research examining the amount and type of carbohydrate consumed is therefore particularly important.
Macon et al. (2023) examined insulin-dysregulated and non-insulin-dysregulated horses receiving small meals of a low-NSC pellet supplemented experimentally with increasing quantities of dextrose or starch.
The study identified possible intake levels at which augmented insulin responses became apparent in insulin-dysregulated horses.
These should be regarded as experimentally observed possible thresholds under the conditions tested, rather than a universal biological cut-off applicable to every feed and every horse.
Importantly, the study investigated orally consumed sugar and starch.
It did not demonstrate that glucose generated progressively from propionate metabolism produces an equivalent postprandial insulin response.
Macon et al. (2024) subsequently studied insulin-dysregulated horses receiving small measured meals of timothy, lucerne or timothy–lucerne forage pellets containing approximately 10% NSC.
Those low-NSC forage pellets did not provoke the augmented insulin response observed with the high-NSC oat challenge (Macon et al., 2024).
This does not prove that beet pulp, soybean hulls or lupin hulls are suitable for every insulin-dysregulated horse.
It does demonstrate why meal composition and carbohydrate source matter.
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Acetate and body-fat production also need context.
We agree that highly fermentable fibres can provide substantial digestible energy.
They can hinder weight loss or contribute to weight gain when total energy intake exceeds requirements.
However, the concept that acetate not immediately used by skeletal muscle simply travels to the liver and becomes body fat is also an oversimplification.
Pethick et al. (1993) demonstrated substantial uptake and oxidation of acetate by equine hindlimb tissues.
Suagee et al. (2010) subsequently investigated de novo fatty-acid synthesis in equine adipose and liver tissues.
Acetate was an important substrate for fatty-acid synthesis in adipose tissue, while equine liver tissue showed comparatively low lipogenic activity under the experimental conditions.
The practical determinant of increasing body fat remains sustained positive energy balance.
Pasture, hay, cereal grain, oil and highly fermentable fibre can all contribute excess calories.
That does not make these energy sources metabolically identical.
But neither does acetate production automatically make a fibre ingredient unsuitable.
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Association does not prove causation.
Shepherd et al. (2014) reported slightly greater plasma acetate concentrations in overweight mares compared with mares in moderate body condition.
However, they found no significant differences in hay digestibility, faecal VFA concentrations or the measured bacterial populations.
The study could not determine whether elevated plasma acetate was:
• a cause of obesity;
• a consequence of obesity; or
• simply associated with altered production, absorption or utilisation.
The mares were not selected according to EMS or insulin dysregulation, and the study did not establish that acetate caused obesity or laminitis (Shepherd et al., 2014).
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What does the evidence actually support?
Taken together, the published research supports the following:
1. Hindgut fermentation supplies horses with substantial usable energy.
2. Acetate is an important oxidative fuel and can also contribute carbon to fatty-acid synthesis.
3. Propionate is an important gluconeogenic substrate.
4. Butyrate is an important energy source for intestinal epithelial tissues and forms part of the normal SCFA profile.
5. Highly fermentable fibres can contribute significant digestible energy and may hinder weight loss or contribute to weight gain when total energy intake exceeds expenditure.
6. Different fibre substrates do not necessarily produce identical acetate:propionate:butyrate profiles.
7. SCFA profiles vary with fibre source, inclusion rate, accompanying diet, microbial adaptation, sampling location, sampling time and the individual horse.
8. The presence of propionate does not, by itself, demonstrate an excessive insulin response.
9. Sugar, starch, meal size and the resulting insulin response remain critical considerations when managing insulin-dysregulated horses.
10. WSC, ESC, starch and fructans should not automatically be treated as physiologically identical carbohydrates.
11. A low-sugar or low-starch feed is not automatically low in calories.
12. Conversely, the normal production of acetate, propionate and butyrate does not automatically make every highly fermentable fibre unsafe for every metabolic horse.
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This is ultimately about the whole diet
The scientifically balanced position is not:
“SCFAs don't matter.”
They do.
Nor should the argument be reduced to:
“Fermentable fibre produces propionate → propionate contributes to glucose production → therefore super fibres are unsafe for metabolic horses.”
The evidence supports a much more nuanced interpretation.
For horses with EMS or insulin dysregulation, we need to assess the complete ration:
ESC/simple sugars + WSC + starch + meal size + total energy + fibre source + fermentation profile + forage and pasture + body condition + exercise + the individual horse’s insulin response.
An appropriately analysed, low-sugar and low-starch fermentable-fibre feed may therefore have a place within a controlled and energy-balanced ration for selected insulin-dysregulated horses.
For an obese, severely insulin-dysregulated or actively laminitic horse, supplementary energy sources require greater justification, stricter control and appropriate veterinary monitoring.
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Conclusion
Equine nutritional physiology is complex.
That complexity is precisely why an average whole-hindgut SCFA ratio should not be applied indiscriminately to beet pulp, soybean hulls, lupin hulls or other highly fermentable fibres as though they all produce identical fermentation and metabolic responses.
Likewise, the Simmons and Ford (1991) finding that approximately 50–61% of glucose production was derived from colonic propionate should not be reversed to mean that 50–61% of all propionate becomes glucose.
Nor should glucose turnover occurring progressively across 24 hours be represented as though that amount of glucose is simultaneously present in the bloodstream.
Highly fermentable fibres are not calorie-free.
They should not be fed without limits.
But neither should a fibre ingredient be declared physiologically unsafe solely because normal hindgut fermentation produces propionate.
Each fibre source and each complete feed needs to be assessed according to its own nutrient composition, feeding rate, sugar and starch exposure, fermentation characteristics, total energy contribution and—most importantly—the response of the individual horse.
One SCFA does not tell us the whole story.
References
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