Pegasus News & Nutrition: A Focus on Fibre

Horse owners will certainly appreciate that, as fibre-fermenting herbivores, horses require large amounts of roughage in their diet – so much so that they are often called ‘hay burners’. But what are the different types of fibre, and how does this influence their digestion? With the cost (and limited availability) of fibre this season, we look at fibre in relation to the equine digestive tract.
In our article on the equine microbiome, we explored the importance of fibre in supporting a healthy and diverse fibro-lytic population in the hindgut of the horse. Looking a little closer at fibre type we can identify several different components, and the solubility of the fibre will affect the rate of digestion and its use for the horse.

Is there NSC in fibre? Non-structural carbohydrates (NSC) are mainly found in the inner cell contents in grain, some hays, and pasture. These are our simple sugars (monosaccharides), such as glucose and fructose, disaccharides (sucrose and maltose), oligosaccharides, fructo-oligosaccharides (fructans), and non-fibre polysaccharides (starch). These NSCs are digested in the small intestine to produce glucose. Whilst starch is mainly found in grains, and starch content of fibre is low, simple sugars are available at varying levels in hay, and fructans are of particular interest when looking at pasture. Therefore, roughage or fibre sources also contain non-structural carbohydrate components.
On the other hand, roughage is also made up of structural carbohydrates, components of the cell wall.

Naturally, these make up the larger portion of roughage and their proportion increases with plant maturity. Structural carbohydrates can be categorised into 2 groups: soluble fibre, such as pectins, gums and mucilages, which are rapidly fermented, and insoluble fibre, such as hemicellulose, cellulose and lignin, which are slowly fermented. Feeds such as lucerne and beet pulp are high in soluble fibre, whilst feeds such as grass and oaten hay tend to be higher in insoluble fibre, with feeds such as straw at the higher end. Both soluble and insoluble fibre is fermented in the hindgut to produce volatile fatty acids as a form of energy for the horse.

Assessing fibre – NDF, ADF, WSC… WT?
From an analysis point of view, there are a number of measures we can look at to assess and classify fibre. Neutral detergent fibre (NDF) includes hemicellulose, cellulose, lignocellulose and lignin. Acid detergent fibre (ADF) includes cellulose, lignocellulose and lignin – the less digestible portions of fibre. Water soluble carbohydrate (WSC) is a measure that includes simple sugars, disaccharides, oligosaccharides and fructans – the sugar components of the fibre. Starch is added to WSC to calculate NSC content. Understanding what these measures mean can be confusing. Your equine nutrition advisor can help to interpret hay or pasture analysis. Horses with a tendency to obesity or temperament issues will often benefit from a hay with a higher slowly fermentable fibre content, which typically contributes less energy. On the other hand, poor doing horses, high performance horses and breeding horses benefit from a portion of high quality, rapidly fermentable fibre in the diet. For horses prone to laminitis, forms of tying up (RER, PSSM etc) a hay with an NSC content <12% is recommended – and don’t forget the pasture factor!

Providing fibre in the diet
For horses, a predominantly roughage diet is ideal. When feeding concentrates, a 70:30 roughage to concentrate ratio is most suited to upholding an optimal microbial environment, and effective digestive function of the hindgut (de Fombelle et al, 2001). Whilst some performance horses can be maintained on a roughage only diet, in our Western Australian climate providing high quality roughage all year round is not always practical, especially in a dry season such as this one. If the bulk of your hay quality is low, it will still provide necessary fermentable fibre for the hindgut micro-flora, and including a small portion of high quality, soluble fibre, such as lucerne, can help offset any energy deficits. High fibre feeds and pellets can be a useful way of providing additional fibre to the diet without hurting the hip pocket.

AllFibre cubes are one such product. It is a fibre-based, low NSC pellet that is great for use to top up fibre in the diet, either as a fibre supplement or partial hay or chaff replacer. Fibre pellets can be a very convenient, easy-to-handle form of roughage that eliminates wastage and storage issues. It contains fibre as a highly digestible energy source and is designed to provide protein and energy levels similar to hay, whilst maintaining a low NSC content.

AllFibre is also great for weight gain as it can be used where an increased volume of roughage intake is required. The low protein, energy and starch content means it can be fed in small amounts to overweight horses on calorie-restricted diets, and is suitable for horses suffering from metabolic disorders, such as EMS, laminitis and Cushing’s Disease.

For more information about fibre types and how best to utilise them in your horse’s diet, contact our nutrition advisor.