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Highly fermentable “Super” fibres – The Good Fibre!

Every bag of Benchmark Horse Feeds is packed with them

Fibre! As nutritionists, we preach the need for its inclusion at no less than 50% of the total daily feed ration. We talk about things like disrupted microbiomes and dysbiosis leading to acidosis, colic, leaky gut syndrome and laminitis when there is insufficient fibre in the diet. We also go on about proper dental (teeth) wear, salvia production, bicarbonate (found in high concentrations in horse saliva) to prevent equine gastric ulcers, improved digestibility and even prevention of colic when there is a good level of fibre in the diet. So, in brief, feed fibre for your horse’s sake (a past article I wrote). But there is a problem with traditional fibre – its relatively low in energy and digestibility.

The average bale of hay contains around 7 to 9 megajoules (MJ) of digestible energy (DE) in 1 kg of dry matter (DM) – DM is what’s left of a feed after all the moisture has been removed. Grains, on the other hand, contain usually between 12 and 15 MJ of DE per 1 kg of DM (almost double!). Therefore, when your horse’s energy requirement increases (like when you increase the level of intensity in your riding), hay alone won’t provide enough energy. Traditionally, in this situation, grain is added to the diet to increase the energy density in the feed – whole oats, boiled barley, processed grain-based feeds, etc. These do increase the energy supply in the diet, but they come with risks. Grains are rapidly digested in the stomach and small intestine, releasing their nutrients for absorption or further digestion. Grains contain very high levels of sugars and starch. Chronic exposure of horses to high levels of sugars has been extensively proven to compromise the immune system and cause various health issues such as insulin resistance (basically equine diabetes), laminitis, and sepsis. Starch, while simply a long chain of glucose (a simple sugar) molecules, their chemical structure makes then 3-times more resistant to digestion than sugars. As such, much of the starch (and there can be a lot of starch in grain – up to 70+% of the grain) ends up the in the microbial fermentative vat called the hindgut (the caecum/colon of the large intestine). A specific type of microbe in the hindgut (Lactate Producing microbes) ferment this starch into lactic acid (hence their name!). This lactic acid causes the pH in the hindgut to fall, dropping from the usual 6.7 pH to below 6.0 pH. When this happens, the “good microbes” in the hindgut, which digest the fibre in the diet, start to die. As they die, they release toxic enzymes called endotoxins which flow into the rest of the digestive system, causing all sorts of issues such as colic, irritable bowel syndrome, leaky gut syndrome, laminitis, etc.

So, you need to increase the energy density in your horse’s feed but now (thanks to reading this article) you are rather concerned by the consequences of feeding too much grain. What can you do? Well, in recent years there has been the development of a special type of feed which has the same benefits of feeding fibre but are much more digestible and, therefore, provide a much higher level of energy density, similar to grains. They are called highly fermentable or “Super” fibres.

What are highly fermentable fibres?

This is where I need to get a little technical for a moment to explain what highly fermentable fibres are. Highly fermentable fibres are complex carbohydrates containing high levels of cellulose, hemicellulose, and pectin which can readily be fermented by the hindgut microbes, but contain much less of the non-digestible lignin than other fibre sources like hay and grass. They also contain high concentrations of readily degradable non-starch polysaccharides (NSP; complex chains of sugars that are not digested in the small intestine but can be fermented in the hindgut but, unlike starch, are not used by microbes to produce lactic acid) that produce large volumes of volatile fatty acids (VFA). These VFA are actually the primary source of energy for a horse, not sugars. VFA; primarily acetate, butyrate and propionate; are high-energy short-chain fats produced by microbes from fibre fermentation that travel safely through the blood (no insulin response unlike sugars) to be converted in the liver to glucose or long-chain fats for storage or used as an immediate energy source. Fats, in fact, contain up to 3-times the energy density of sugars!

In the past, to increase the concentration of energy in the horse’s diet it was necessary to replace some of the low-energy hay with higher-energy, high-starch grains. The introduction of highly fermentable “Super” fibres may be able to replace much of this grain in the diet as an alternative energy source. How much extra energy these fibres provide is unsure as the current measures of DE are reasonably accurate for feed products like hay and grain-based feeds, but they may substantially underestimate the DE for highly fermentable feeds which contain over 35% crude fibre and a high concentration of NSP. This could mean that some highly fermentable “Super” fibres may have a similar DE value as oats and barley, or even more! Studies both in the US and Europe have shown that horses fed a diet consisting of just hay and highly fermentable “Super” fibres were able to perform at all levels of energy exertion, including racing, and that yearlings feed a similar diet grew as well as those on traditional high grain diets.

Soybean hulls – A highly fermentable “Super” fibre

Soybean hulls are simply the seed coat of the soybean that have been removed from the bean during the oil extraction process. They are high in pectin as well as other soluble fibres including NSP, making them readily fermented by the microbes in the hindgut. They are low in sugars and starch meaning there is little risk of health issues such as acidosis and leaky gut syndrome and great for horses prone to laminitis and colic. Soybean hulls are a common ingredient in many of the “grain-free” feeds you find at your feed store today.

Studies have shown that most of the soybean hulls eaten by the horse are digested through microbial fermentation, meaning very little is wasted. Studies have also shown that the inclusion of soybean hull in a horse’s diet greatly increases the amount of VFA produced, particularly propionate which favours the formation of glucose in the liver. In fact, soybean hulls were found to be so readily digested in the hindgut, producing such high quantities of VFA and increasing the population of the beneficial fibre-digesting microbes that it has been suggested they can replace up 75% of the total fibre in the diet and could be a suitable replacement for many grains and grain-based feeds used to traditionally increase the energy density of the feed.

Benefits of feeding highly fermentable “Super” fibres

I’ve already covered many benefits for feeding highly fermentable “Super” fibres to your horse – chewing, saliva, proper teeth wear, gut health, low sugars and starch, high potential energy, highly digestible, etc. There are some other reasons for including these types of feed in your horse’s diet too. Some horses cannot physically eat enough hay to fulfil their fibre requirements so, the inclusion of a highly fermentable “Super” fibre like Soybean Hulls deals with that issue. Some horses require a steady source of energy for long distances and high energy, highly fermentable “Super” fibres can provide this sustained energy supply while also acting as a water reservoir to prevent dehydration. There are also horses that cannot tolerate high sugar and starch diets, particularly those prone to laminitis, IR, exertional rhabdomyolysis (tying up), and PSSM. These horses often find relief when fed a low starch feed such as Soybean Hulls.

Benchmark Feeds and Highly Fermentable “Super” Fibres

At Benchmark Feeds, highly fermentable “Super” fibres in the form of Soybean Hulls form the basis of each and every feed. Benchmark feeds understand that a horse needs to live and eat like a horse, meaning fibre is the most important ingredient in each and every horse’s diet. They also understand that sometimes, traditional fibre sources cannot supply enough energy, protein and other nutrients needed to perform at their best. Knowing that too much sugar in the diet is one of the main health problems experienced by horses today, all Benchmark feeds contain highly fermentable “Super” fibre Soybean Hulls of only the highest quality, sampled and analysed with each batch to ensure only the highest quality of product is made available for you, the customer and, more importantly, your horse!

Dr Mark Barnett (PhD)
MTB Equine Services
Equine Nutritional Consultant to Benchmark Feeds