This is going to be the nerdiest equine nutrition article that I've ever written. As I sit here typing, I know that very few people will read it, but I'm ok with that. Article writing, as well as the monthly guest lectures, are ways in which I continue to sharpen my craft, avoid becoming stagnant, and challenge my way of thinking about horse diets. This week I'm diving really deep into fiber supplements for horses, or more specifically, the "middle carbohydrates" that are being marketed to prevent sand colic and gastric ulcers- namely fructo-oligosaccharides, gums, pectins, mucilages (beta-glucans), and psyllium. In traditional equine nutrition education, there is rarely more than an honorable mention of these middle carbohydrates. However, they are significant parts of all plant cells and influence the horse's digestion of those plants. If that sounds interesting to you, then let's start with a more clear definition of these middle carbohydrates that play such a big role in your horse's health and compare the options available to you in the marketplace.
DEFINITION BY WAY OF INTRODUCTION
If you've been a horse owner/feeder for five minutes, you've heard that sugars and starches are to be avoided and you probably have some vague notion about the benefits of complex fiber. However, I would wager a bet that many of you have never pondered the value of what I'm calling the "middle carbohydrates".
Why do I call them the "middle carbohydrates? Well, I make sense of this massive molecular category called "carbohydrates" by imaging them lined up on a spectrum. This spectrum is measured in complexity (*see image below); from left to right- the number of saccharide (sugar) molecules goes up as does the complexity of bonds linking them together. On the far left side of this spectrum are the monosaccharides (i.e. glucose, fructose, galactose). Then, moving along the spectrum are the oligosaccharides and starch. Monosaccharides, oligosaccharides, and starch are the most simple carbohydrates which means that they are the easiest to digest and enzymes can do some of the work breaking them down. On the far right side of this spectrum are hemicellulose, cellulose and ligno-cellulose which are made of MANY saccharides linked together in increasingly more complex ways which makes them much harder to digest. The horse needs many billions of "bugs" in their cecum and colon to digest these complex carbohydrates. Between the very simple carbohydrates (sugars/starches) and the very complex carbohydrates (cellulose), in the middle of this spectrum, are the middle carbohydrates like fructan, mannan-oligosaccharides, pectins, beta-glucan, and psyllium. It's these middle carbohydrate (a.k.a. polysaccharides) that are most often used in fiber supplementation or fiber therapy!
Measurements of middle carbohydrates are hard to find. You won't see them listed in a forage analysis. They are there, but imbedded within the non-fiber carbohydrate, soluble fiber, non-starch polysaccharide, and even the non-structural carbohydrate results. So, yea, they are sneaky buggers. However, as you'll see later on in the fiber supplement comparison chart, some companies will report the amount of polysaccharide in grams. For example, the psyllium supplements on the market today contain between 100 to 140 grams of psyllium seed husk (powder) per serving for a 1,000 lb horse.
The best way to organize these middle carbohydrates is to consider their behavior in the digestive system. The functionality of these carbohydrates is, after all, what we are interested in. We'd like these polysaccharides to either protect the epithelial tissue of the GI tract, moderate inflammation, change the consistency of feces, and/or positively change the micriobiota of the horse. Because there are multiple stories that can be told by these middle carbohydrates, it's important to differentiate and delegate their tasks. McRorie (2015) did this best in a paper titled "Evidence-Based Approach to Fiber Supplements and Clinically Meaningful Health Benefits, Part 1" in Nutrition Today. He describes four properties of fiber that affect their behavior in the GI tract; solubility, rate of fermentation, viscosity, and gel formation. Distinguishing each polysaccharide's physical properties is needed to understand which supplements may help your horse's condition whether it be irritable bowel syndrome, ulceration, diarrhea or sand colic.
Psyllium- soluble and insoluble, viscous, gel forming, non-fermented
Pectin- soluble, viscous, gel forming, readily fermented
Beta glucan (mucilage)- soluble, viscous, gel forming, readily fermented
Mannan-oligosaccharides (MOS)- soluble, non-gel forming
Inulin- soluble, nonviscous, non-gel forming, readily fermented
Let's highlight some basic properties of these "middle carbohydrates".
Psyllium
You'll recognize psyllium as the ingredient of Metamucil which is used to treat constipation. McRorie (2015) showed health benefits in humans.
In the equine marketplace, supplement claims target prevention of sand colic.
The raw ingredient comes from the seed husk of a plant called Plantago ovata.
soluble, viscous, gel forming, non-fermented (but adaptable)
contains hemicellulose, so more difficult to digest, but not completely
A very important study in 1998 by Hammock et. al. showed no apparent effect of pysllium mucilloid on sand evacuation. However, it's heavily used today in veterinary clinics and home use.
If you have a serious sand accumulation problem in your horse's GI tract, research suggests daily clinical naso-gastric tubing is much more effective than at-home supplementation (Kaikkonen et.al., 2016).
Studies supplemented 0.31g/kg of BW (Po et. al., 2023) up to 1g/kg BW (Kaikkonen et al., 2016) which is 155 to 500 grams of psyllium husk.
Common supplements offer 100-140 grams of psyllium seed husk per serving for 1,000 lb horse.
Short periods of use are important, because equine microbiome may adapt over time and lessen the effects (Po et. al., 2023).
Psyllium may lower mean postprandial blood glucose and peak blood glucose in horses (Moreaux et. al., 2011).
Pectin
You'll recognize pectin as a common kitchen ingredient for making jams and jellies. This is different from gelatin which comes from animal collagen.
In the equine marketplace, pectin supplement claims target prevention of gastric ulcers.
However, a study by Woodward et. al. (2014) showed no significant decrease in ulcer scores when feeding a supplement rich in pectin.
Pectin is extracted from citrus pulp (29%) and apple pulp (Silva et. al., 2016).
Common equine feed ingredients that contain significant amounts of pectin include beet pulp (20%), soybean hulls (33.7%), and alfalfa hay (10.5-14.2% of DM) (Hansen et. al., 2020; Silva et. al., 2016; Wang et. al., 2020).
The above common feed ingredients are relatively high in calories due, in part, to the high fermentation rate of pectin (Cipriano-Salazar et. al., 2019). Pectin rich ingredients can be used to replace starch in the diet.
Potential benefits include increased pH, increased digestible energy, and increased viscosity of the feed passing through the GI tract (Silva et. al., 2016).
A pectin supplement called EquiTop ProNutrin suggests feeding 0.55 lb of their citrus pulp based product for an 1,000 lb horse which seems reasonable and significant.
Beta-Glucans (mucilage)
You'll recognize beta-glucan as the molecule in oatmeal that gives it a gel-like consistency.
soluble, viscous, gel forming, readily fermented
Beta-glucan in horse supplements mostly comes from oats or mushrooms.
You'll recognize products on the marketplace such as 100X Equine Gut X, SUCCEED Digestive Conditioning and Relyne GI by Hagyard.
In the equine marketplace, beta-glucan rich products claims target gastric ulcers.
Three notable studies using beta-glucan rich products have shown promising results; 1 in rats and 2 in horses (Matsumoto et. al., 2002; Andrews et. al. White Paper, and Slovis, 2017). The quality of the Slovis (2017) study is poor as they had no control group, were relying on owner compliance, environment and treatment amounts varied. However, the White Paper by Andrews et. al. used 12 thoroughbred horses with a control group and a masked investigator (blind ulcer scorer).
Inulin
Not a common ingredient in horse supplements, but you'll find it at the bottom of some feed labels such as Uckele GUT Powder, Foran Equine B- Complete and several Cavalor products.
I'm not particularly interested in inulin, so I didn't as deep into this ingreidnet as others, but I did come across a study by Coenen et. al. (2006) that suggests inulin may be digested similarly to starch. The rapid fermentation of this polysaccharide is less useful in equine fiber therapy except then high energy for weight gain/maintenance are necessary.
soluble, nonviscous, readily fermented
long chain fructo-oligosaccharide, found in chicory root, barley and oats
Johnson et al. (2015) found no affect on glycemic response in humans
Mannan-oligosaccharide (MOS)
These MOS products are everywhere in your horse feeds and supplements! You might check your labels to see if you are already feeding it ;)
In the equine marketplace, supplement claims focus on immune modulation.
There is a plethora of evidence for use of this "middle carbohydrate" in many species, so I will spare us both the long list of references.
SUMMARY
The idea of isolating individual carbohydrates (polysaccharides) from plants, yeast and fungi and feeding them as supplements to horses is an interesting idea, but research has shown it may be worth the effort. There are, of course, many more polysaccharides in our horse's diets, but these are the ingredients that have been filtered out by research, availability, cost, and a company's passion to market it.
These middle carbohydrates have a wide range of traits and useful modes of action including energy creation, immune modulation, and positive hindgut ecology changes.
Here's my number one take-away; in order for fiber supplements to be truly effective as a prebiotic, they need to be largely non-fermentable and increase viscosity (create a gel). Feeding rapidly fermented polysaccharides such as pectin and inulin are not worth the cost, because they are already high in readily available ingredients such as beet pulp and soybean hulls. However, the physical gelling properties of polysaccharides such as psyllium and beta-glucan could be beneficial to your horse. I think this particularly true if your primary forage sources are not ideal and management is poor.
Would I use any of these supplements, you might ask. Yes. If my horse was suffering from sand colic, I would assuredly use a psyllium product due to it's low cost and safetly. If my horses' immune systems were challenged, I'd make sure to add a mannan-oligosaccharide product. And, if my horse was suffering from repeated ulcers, I'd consider a beta-glucan rich product once all of my forage first options had proven futile.
REFERENCES
Andrews, F.M., S. Mordoh, M.L. Keowen, and F. Garza Jr. Effects of Relyne GI with Beta-Glucan (TBG136TM) on Stomach Health [White Paper]. Retrieved August 2024 from https://www.resolvet.com/files/LSU-Final-White-Pager.pdf.
Britannica, T. Editors of Encyclopaedia (2024, October 11). lignin. Encyclopedia Britannica. https://www.britannica.com/science/lignin
Coenen, M., A. Mo¨ßeler, and I. Vervuert. 2006. Fermentative Gases in Breath Indicate that Inulin and Starch Start to Be Degraded by Microbial Fermentation in the Stomach and Small Intestine of the Horse in Contrast to Pectin and Cellulose. American Society for Nutrition. J. Nutr. 136: 2108S–2110S.
Cipriano-Salazar, M., Adegbeye, M.J., Elghandour, M., Barbasoa-Pilego, A., Mellado, M., Hassan, A., and A. Salem. 2019. Journal of Equine Veterinary Science. 74:103-110.
*Hammock, P.D., D.E. Freeman, and G.J. Baker. 1998. Failure of psyllium mucilloid to hasten evaluation of sand from the equine large intestine. Vet Surg. Nov-Dec;27(6):547-54. doi: 10.1111/j.1532-950x.1998.tb00530.x. PMID: 9845218.
*Hansen, T.L., E.M. Rankins, J.M. Bobel, M. McKinney, T.J. Hackmann, and L.K. Warren. 2020.
Postprandial Blood Glucose and Insulin Responses of Horses to Feeds Differing in Soluble Fiber Concentration. Journal of Equine Veterinary Science. Volume 88. 102963,
ISSN 0737-0806 https://doi.org/10.1016/j.jevs.2020.102963.
Hotwagner, K. and C. Iben. 2008. Evacuation of sand from the equine intestine with mineral oil, with and without psyllium. J Anim Physiol Anim Nutr (Berl). Feb;92(1):86-91. doi: 10.1111/j.1439-0396.2007.00713.x. PMID: 18184383.
*Kaikkonen, R., K. Niinisto, T. Lindholm, and M. Raekallio. 2016. Comparison of psyllium feeding at home and nasogastric intubation of psyllium and magnesium sulfate in the hospital as a treatment of naturally occurring colonic sand (geosediment) accumulations in horses: a retrospective study. Acta Vet Scand. 58:73.
McRorie, JW Jr. 2015. Evidence-Based Approach to Fiber Supplements and Clinically Meaningful Health Benefits, Part 1: What to Look for and How to Recommend an Effective Fiber Therapy. Nutr Today. Mar;50(2):82-89. doi: 10.1097/NT.0000000000000082. PMID: 25972618; PMCID: PMC4415962.
Moreaux, S.J., J.L. Nichols, J.G.P. Bowman, and P.G. Hatfield. 2011. Psyllium Lowers Blood Glucose and Insulin Concentrations in Horses. Journal of Equine Veterinary Science. Volume 31(4):160-165. ISSN 0737-0806, https://doi.org/10.1016/j.jevs.2011.02.002.
*Po, B.T., J.M. Campos-Krauer, K.E. Sullivan, L.K. Warren, and D. Vyas. 2023. 97 Effect of psyllium husk supplementation on equine fecal nutrient composition and in vitro fermentation. Journal of Equine Veterinary Science. Volume 124/ 104399, ISSN 0737-0806, https://doi.org/10.1016/j.jevs.2023.104399.
Sanz, M.G., A. Viljoen, M.N. Saulez, S. Olorunju, and F.M. Andrews. 2014. Efficacy of a pectin-lecithin complex for treatment and prevention of gastric ulcers in horses. Vet Rec. 175(6):147. doi: 10.1136/vr.102359. Epub 2014 May 12. PMID: 24821856.
*Silva, R. H. P., Rezende, A. S. C. de, Inácio, D. F. da S., & P. González-Redondo. 2016. Pectin-rich by-products in feeding horses—A review. Cogent Food & Agriculture, 2(1). https://doi.org/10.1080/23311932.2016.1193925
Slovis, N. 2017. Polysaccharide treatment reduces gastric ulceration in active horses. Journal of Equine Veterinary Science. 50:116-120.
Smith., H. S. Grant, J. Parker and R Murphy. 2020. Yeast cell wall mannan rich fraction modulates bacterial cellular respiration potentiating antibiotic efficacy. Scientific Reports. 10:21880. https://doi.org/10.1038/s41598-020-78855-5.
*Wang, B, Sun Z, Yu Z. 2020. Pectin Degradation is an Important Determinant for Alfalfa Silage Fermentation through the Rescheduling of the Bacterial Community. Microorganisms. 8(4):488. doi: 10.3390/microorganisms8040488. Erratum in: Microorganisms. 2020 May 20;8(5):E769. doi: 10.3390/microorganisms8050769. PMID: 32235428; PMCID: PMC7232347.
Woodward, M.C., N.K. Huff, F. Garza Jr., M.L. Keowen, M.T. Kearney, and F.M. Andrews. 2014. Effect of pectin, lecithin, and antacid feed supplements (Egusin) on gastric ulcer scores, gastric fluid pH, and blood gas values in horses. BMC Veterinary Research. From Eleventh International Equine Colic Research Symposium Dublin Ireland. 7-10 July 2014. 10 (Supp 1):54. http://www.biomedcentral.com/1746-6148/10/51/54.
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