Feeds that provide high Digestible Fibre and low NSC for horses
Fibre, also known as roughage, is the structural part of the plant that gives the frame rigidity. There are a few types of fibre and of these fibres the ones that are important to note for horse feeds are; cellulose, hemicelluloses, lignin and pectin. These types of fibre are types of carbohydrate made up of many glucose molecules bound by links that are indigestible to mammals. Horses however, have evolved to break these links through enlargement of the colon to form the caecum. The caecum houses micro organisms that are specialised in breaking the links making up fibre, making the glucose available for a ready source of energy for the horse. It must be noted horses cannot digest lignin and can only partially digest cellulose and hemicelluloses.
On feed labels fibre is seen as "crude fibre", this includes some cellulose and lignin. Other terms that are important in the assessment of the digestibility of a feed, are the terms ADF and NDF. ADF stands for acid detergent fibre which describes the portion of the feed that is cellulose and lignin whereas NDF stands for neutral detergent fibre and represents the part of the feed that is lignin, cellulose and hemicelluloses. The higher these values, the less digestible the feed is.
Fibre in the Horses Diet
Fibre remains an important part of the horses diet simply because the horses digestive tract is designed for digestion of fibre. If the microbial organisms living within the caecum of the horse are not exposed to fibre on a regular basis then they begin to die of therefore releasing toxins into the bloodstream resulting in enterotoxaemia leading to laminitis. From the behavioural aspect, horses naturally have the urge to graze and forage for long periods of time and this behaviour is normally suppressed by horses being kept in stalls and stables etc. Vices can develop if the horse isn't allowed to graze but this behaviour can be substituted for by supplying long stem forages.
When fibre is broken down in the caecum by the microbial organisms they release volatile fatty acids (mainly acetate, propionate and butyrate). Upon absorption, these fatty acids can be used as immediate sources of energy for the horse, or be converted to fats for storage. Studies have revealed that horses derive a lot of energy from these volatile fatty acids when their diets consist of mainly forages. The reason that many people shy away from keeping their horse on high fibre diets, is that the by-product of fibre digestion is heat and gas. This takes energy away from the horse and so people have moved to starches as they provide more energy per unit of weight. Starches however have proved to be detrimental to a horse when consumed in large amounts as high levels of NSC causes many metabolic disorders and is a large factor in laminitis (number one killer of horses) and insulin resistance. Oils and fats however, are more energy dense than starches and do not cause any metabolic disorders and can in fact, improve a horses condition and health.
Low NSC Feeds