When discussing horse feed, fiber content is often one of the first values people look at on the feed label.
But two feeds can contain almost the same amount of fiber and still behave very differently in the horse’s digestive system.
The reason is simple:
fiber is not a single nutrient.
Plants contain many different types of fiber and carbohydrate structures. They differ in how well they are fermented in the horse’s gut, how much water they bind, and what physical properties they have.
That is why the crude fiber percentage alone tells us relatively little about what kind of fiber the horse is actually receiving.
Horses are designed to use fiber
The horse is a hindgut fermenter.
A large proportion of plant fiber in the diet passes into the cecum and colon, where gut microbes break it down through fermentation. This process produces, among other things, short-chain fatty acids that the horse can use as a source of energy.
Fiber is therefore not simply “bulk” passing through the digestive tract. It is a central part of the horse’s energy metabolism and the microbial ecosystem of the gut.
At the same time, the physical structure of forage has an important role of its own.
Eating long-stem forage requires a great deal of chewing. Chewing increases saliva production, prolongs feeding time, and supports normal digestion and natural feeding behavior.
That is why the foundation of horse feeding remains:
a sufficient amount of good-quality forage.
Different fiber supplements can complement the diet, but they do not replace hay or pasture.
Structural fiber – the foundation of the diet
In hay and other forages, much of the fiber consists of plant cell wall components such as cellulose, hemicellulose, and lignin.
These are commonly described in forage analyses using values such as NDF and ADF.
Structural fiber affects, among other things:
- chewing and saliva production
- the amount of time the horse spends eating
- gut fill
- normal intestinal motility
- fermentation in the hindgut.
However, not all structural fiber is the same.
As plants mature and become more fibrous, their cell walls generally become increasingly lignified. Gut microbes are largely unable to break down lignin, and the digestibility of the other cell wall components may decrease at the same time.
This is why two hay samples with similar fiber values on paper can be quite different in practice.
Fermentable fibers – fuel for gut microbes
Some fiber sources are fermented much more readily than highly lignified plant fiber.
Examples include many pectin-rich ingredients and beet pulp.
These ingredients are widely used in horse diets because they can provide energy through microbial fermentation without requiring the same amount of starch-rich grain.
This is a good example of why fiber percentage alone does not tell us the nutritional value of that fiber.
Two fiber sources may appear similar in an analysis, while one may be considerably easier for hindgut microbes to utilize.
What about soluble and gel-forming fibers?
Some plant carbohydrates behave very differently in water compared with the coarse structural fiber found in hay.
They can:
- bind large amounts of water
- swell
- form a viscous or gel-like mass
- also serve as fermentable material for gut microbes.
Good examples include chia, psyllium, and pectin.
It is also useful to mention inulin in this context, even though its key property is not gel formation but its fermentation by gut microbes.
Chia – much more than just fiber
The outer surface of chia seeds contains large amounts of water-binding mucilage compounds.
When chia comes into contact with water, a gel-like layer quickly forms around the seed. This can easily be seen at home: chia seeds swell strongly in water and develop a mucilaginous coating.
Because of these properties, chia is now widely used in horse feeding to support the movement of sand through the intestine, and it is also recommended in practice by veterinarians.
What makes chia especially interesting, however, is that it is not simply a fiber ingredient used in connection with sand.
Whole chia seeds also contain:
- high levels of alpha-linolenic acid, the omega-3 fatty acid ALA
- high-quality plant protein
- several different fiber fractions
- water-binding mucilage
- naturally occurring nutrients.
Chia can therefore be used as part of the horse’s daily diet and not only as a short-term course.
In the same ingredient, gel-forming fiber is combined with valuable nutritional properties.
The use of chia to support sand clearance has become increasingly common in practice.
Psyllium – a highly swelling fiber
Psyllium, or psyllium husk, contains very high levels of water-binding polysaccharides.
When psyllium comes into contact with water, it swells quickly and forms a highly viscous gel.
This is why psyllium is one of the most traditionally used products for sand clearance in horses.
There are also studies in horses, although the results are not entirely consistent.
In some studies, psyllium alone or products containing psyllium did not remove sand more effectively than management changes and keeping the horse in a sand-free environment. In horses with larger sand accumulations, better results have been achieved, for example, with a combination of psyllium and magnesium sulfate administered by a veterinarian via nasogastric tube.
Psyllium therefore has an established role in sand clearance, but treating a serious sand accumulation is not the same as preventive fiber feeding.
Pectin – a particularly interesting fiber for the stomach and gut
Pectin is a polysaccharide found in plant cell walls and occurs naturally in fruits and many plant-based feed ingredients.
It differs in several ways from the coarse structural fiber found in hay.
Pectin:
- binds water
- can form gel-like structures
- is readily fermented
- serves as a substrate for microbes in the hindgut.
Pectin is also interesting in horse feeding because it is commonly used in feed formulations designed to support gastric wellbeing.
Pectin, and especially pectin-lecithin combinations, have also been studied in horses in connection with changes in the gastric mucosa.
Pectin-lecithin combinations have produced promising results in equine studies. In some studies, horses receiving the combination showed a reduction in gastric mucosal lesions, supporting its use in feed formulations intended to support gastric wellbeing. However, study designs have differed, and the effect has not been demonstrated under all conditions, such as experimental models involving prolonged fasting.
The physiological properties of pectin are nevertheless particularly interesting: the same fiber can bind water and form gel-like structures while later serving as fermentable substrate for gut microbes.
Inulin – prebiotic fiber that feeds microbes
Inulin is a somewhat different type of fiber.
Its main characteristic is not strong water binding or gel formation, but the fact that gut microbes are able to ferment it.
Inulin belongs to the fructans and is often used as a prebiotic fiber.
In practice, a prebiotic is a compound that the host animal does not digest in the same way as, for example, starch, but which certain gut microbes are able to utilize.
Studies in horses have shown that inulin and fructooligosaccharides can influence microbial fermentation in the digestive tract. At the same time, research also shows that the relationship is not as simple as “more prebiotics = a better gut.”
Some inulin and fructans may be fermented before reaching the hindgut, and large amounts of rapidly fermentable carbohydrates can strongly alter conditions in the digestive tract.
Therefore, the amount used, the ingredient itself, and the overall composition of the diet all matter when it comes to prebiotic fibers.
Four fiber sources – very different properties
Chia, psyllium, pectin, and inulin can all be described as fiber-related ingredients, but in practice their properties are very different.
Chia
→ water-binding mucilage together with nutritionally valuable omega-3 fatty acids, protein, and other fibers
→ used both in daily feeding and to support the movement of sand through the intestine
Psyllium
→ a highly swelling fiber that forms a viscous gel
→ especially well known for its use in sand clearance
Pectin
→ a readily fermentable and water-binding fiber with gel-forming properties
→ interesting from both a gastric and hindgut perspective
Inulin
→ a readily fermentable prebiotic fiber
→ primarily of interest because of its role in microbial fermentation in the gut.
This comparison alone shows why the word fiber by itself tells us relatively little about a feed.
Why crude fiber percentage does not tell the whole story
The crude fiber value shown on a feed label is determined using a specific analytical method.
It does not directly tell us:
- where the fiber comes from
- how well it is fermented
- how much soluble fiber it contains
- how much gel-forming polysaccharide it contains
- how much water it binds
- how quickly gut microbes can utilize it
- what other nutrients the fiber source contributes.
This leads to one of the most important points of the article:
15% crude fiber in one product does not necessarily mean the same thing nutritionally as 15% crude fiber in another.
The source of the fiber matters.
Horses do not need one “best” type of fiber
Different types of fiber should not be ranked simply as better or worse.
They have different functions.
Long-stem forage supports chewing, saliva production, normal feeding behavior, and digestive tract function.
Fermentable fibers provide energy for gut microbes and, through fermentation, produce compounds that the horse itself can use.
Gel-forming fibers can bind large amounts of water and behave very differently in the digestive tract compared with coarse plant fiber.
Prebiotic fibers primarily influence what type of fermentable substrate is available to microbes in the digestive tract.
So a better question than
“How much fiber does this product contain?”
is:
“Which fiber sources make up that amount, and what properties do those particular fibers have?”
Good forage still forms the foundation
Specialized fiber sources can complement a horse’s diet in many different ways.
Chia, psyllium, pectin, inulin, beet pulp, and many other fiber sources can all be useful in the right situation.
But they do not change the horse’s basic physiology.
The horse’s digestive system evolved to consume small amounts of fiber-rich plant material throughout much of the day.
That is why good fiber feeding always begins with a sufficient amount of high-quality forage.
After that, we can consider which additional types of fiber may be useful in the horse’s diet – and, most importantly, why.
References
Zeyner A. et al. In Vitro Gas Production from Batch Cultures of Stomach and Hindgut Digesta of Horses Adapted to a Prebiotic Dose of Fructooligosaccharides and Inulin. Journal of Equine Veterinary Science, 2020.
Hotwagner K. & Iben C. Evacuation of sand from the equine intestine with mineral oil, with and without psyllium.
Niinistö K. et al. Comparison of the effects of enteral psyllium, magnesium sulphate and their combination for removal of sand from the large colon of horses.
Niinistö K. et al. Investigation of the treatment of sand accumulations in the equine large colon with psyllium and magnesium sulphate.
Murray M.J. & Grady T.C. The effect of a pectin-lecithin complex on prevention of gastric mucosal lesions induced by feed deprivation in ponies.
Venner M. et al. Treatment of gastric lesions in horses with pectin-lecithin complex.
