Hemp Hulls – A Quality Highly Fermentable Fibre

Fibre! Us nutritionists 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. But there is a problem with fibre which can negatively impact on the performance of a horse – 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 – 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. 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 (IR), laminitis, and even sepsis.

Starch is far more resistant to digestion in the small intestine so much of it ends up the in the microbial fermentative vat called the hindgut (the caecum/colon of the large intestine). A specific type of microbes in the hindgut (Lactate Producing microbes) ferment this starch into lactic acid. This lactic acid causes the pH in the hindgut to fall. 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 how do you increase the energy density in your horse’s feed without the consequences of feeding too much grain? Well, in recent years there has been the development of a special group of feeds 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 fibres.

What are highly fermentable fibres?

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 (complex chains of sugars that are not digested in the small intestine but 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 either 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 sugar and starch grains. The introduction of highly fermentable 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 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 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.

Hemp seed hulls are one such highly fermentable fibre. Hemp plant production has shown a steady growth in worldwide production in recent years. Containing over 30% crude fibre, virtually no sugars or starch, and often over 20% crude protein, hemp hulls are a quality horse feed. Having a very high fat content coupled with plenty of highly fermentable fibre, the DE of hemp hulls is about 20 MJ per kilogram of DM (nearly double that of oats without the sugar issues). They do contain a few anti-nutritional factors but still, with such high energy and protein, they have the potential to be a quality highly fermentable fibre.

The inclusion of a quality probiotic would also increase the benefits to the horse in eating a highly fermentable fibre like hemp hulls. Probiotics are live micro-organisms which improve/enhance the nutrient outcome and health of a horse. Including a quality probiotic, like Saccharomyces cerevisiae, to the horse’s diet will likely improve the digestibility of the hemp hulls within the digestive tract plus provide further, non-nutritional benefits to the animal. A good probiotic can enhance the overall health of a horse through regulation of the microbial population (the microbiome) within the gut, influencing the types and quantity of hormones and enzymes released. These hormones and enzymes play a bigger role within the animal than just getting more out of the feed. They often are key components in the normal physiological functions of the animal, even influencing mood and behaviour.

Benefits of feeding highly fermentable fibres

There are many benefits in feeding a highly fermentable fibre like hemp hulls to your horse such as increased chewing and saliva production, proper teeth wear, gut health, low sugars and starch, high potential energy, high digestible, etc. There are some other reasons for including this type of feed in your horse’s diet too. Some horses cannot physically eat enough hay to fulfil their fibre requirements so, the inclusion of some highly fermentable fibre deals with that issue. Some horses require a steady source of energy for long distances and high energy. Highly fermentable 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 a highly fermentable fibre like hemp hulls.

It is recommended that a quality balancing supplement be used to correct any nutrient deficiencies and ratio imbalances but, overall, highly fermentable fibres can increase the energy content of a horse’s diet while having positive effects on gut and overall health.

Dr Mark Barnett PhD

MTB Equine Services

www.mtbequine.com