Fibre
Not all fibre is created equal and, depending on its origins, it can vary widely in terms of quality and digestibility.
What is fibre?
Fibre consists of three main substances: cellulose, hemicellulose and lignin.
Lignin is the very hard fibre that gives plant material its rigidity. By way of illustration, trees are very high in lignin, whereas tender young grass is very low. Lignin is considered 100% indigestible by horses and it also cannot be fermented by the bacteria that they harbour in their digestive tracts.
Cellulose, and to a certain extent hemicellulose, however, are digestible, and it is from these two that horses derive most of their digestible energy requirements.
Cellulose and hemicellulose, which stem from the non-seed and non-fruit portions of a plant (such as the leaves, stems and hulls), are also are known as insoluble fibre.
Soluble fibre (which makes up a relatively minor portion of the fibre in a horse’s diet) is fibre stemming from the ‘liquid’ portions of a plant: the resin, sap, pectins and mucilages.
All plant-eaters use nearly all of the soluble fibre they ingest, but the degree of insoluble fibre that horses use varies.
The sooner bacteria go to work in breaking the beta-bonds in the fibre, the higher the percentage of the insoluble fibre that is used by the horse.
Importantly, however, even the insoluble fibre that is not digested plays a significant role in the equine diet. This non-digested fibre helps to maintain gut motility and function, as well as preventing too-rapid consumption of carbohydrates, which are readily digested and can sometimes cause digestive upset if not ‘buffered’ by the presence of fibre in the colon.
Fabulous fibres
No matter the breed or intended use, all horses require fibre in their diets at an inclusion of at least 1.5% of body weight per day, with an absolute minimum of 1% per day in extreme conditions. According to the National Research Council’s Nutrient Requirements of Horses (2007, 6th Edition), a large body of evidence suggests that insufficient dietary fibre can lead to several digestive issues (such as colic) and behavioural vices (such as cribbing) in horses. Horses’ fibre needs are met most commonly by pasture and hay, and most of the time, provided horses have access to one or the other of these 24 hours a day, their fibre intake will be adequate. If supplies are not adequate, other fibre sources can be incorporated as discussed in a later article in this guide, on Forage Extenders.
REFERENCES:
www.thehorse.com/articles/29567/alternative-fiber-sources-for-horses written by Kirsten M JanickiI al.