Why Is Fibre so Important

Portrait of beautiful chestnut horse eating grass

Horse grazing

If you Google ‘Why is Fibre Important?’ you get bombarded with frightening  facts about your diet and fibre – ‘Fibre is an important part of a balanced diet’, ‘it can help prevent heart disease, diabetes, weight gain, and some cancers’, ‘it can improve digestive health’ – but what about your horse?  What is fibre?  How important is fibre? What are the types of fibre and what happens if your horse has a low fibre diet?

The horse’s digestive tract evolved from an animal that lead a relatively sedentary lifestyle continually browsing for fibre-rich and low starch food.  They could spend at least 16 hours grazing per day and despite over 2000 years of domestication the modern horse is still designed to be trickle fed ‘little and often’. The digestive tract is huge and takes up approx. 15% of the horse’s total weight.  It starts with the teeth and chewing.

Unlike humans, a horse will only produce saliva when chewing, the saliva has a buffering effect so more chewing will produce more saliva which will have a neutralising effect on the contents of the stomach and help reduce the risk of stomach ulcers.  So if chewing is important then horse owners need to consider this when looking at their horse’s diet;

Feed type Amount Time spent chewing
Hay 1kg 20mins
Compound 1kg 8 mins


The horse’s stomach is small and in text books it is described as a small rugby ball.  Less than 10% of digestive capacity is carried out in the stomach.  Although fibre is not digested in the stomach fibre plays an important role in preventing squamous ulcers.  It is recommended that horses are exercised after being given access to fibre as this fibre can be a layer on top of the stomach acid so help prevent acid splashing on the top part of the stomach and causing erosion.

Horse Digestive System - Horse Anatomy

Horse Digestive System – Horse Anatomy

Horses are herbivores and are classed as ‘hindgut fermenters’.  No animal can digest fibre alone,  it requires bacteria and micro-organisms.  The hindgut comprises of the caecum and the large intestine and this is where microbial fermentation takes place.  It is two-thirds of the digestive system and highlights what an important role fibre is in the horses diet.

As the micro organisms break the fibre down they produce Volatile Fatty Acids (VFAs) which the horse utilises as an energy source.  This process also generates B vitamins which are a group of vitamins important for energy transfer within the body (although many horse owners will think of Biotin which is a B Vit beneficial in promoting good hoof quality).  A horse on a fibre rich diet normally produces sufficient B Vits and does not require B Vits supplements.

Another important factor of fibre fermentation is it produces heat to help keep the horse warm – as we are coming into winter this is an important factor to consider to ensure your horse is warm during the British cold and wet winter.

Looking at the horses digestive system we can understand that fibre is very important but the type of fibre is also an important factor when looking at a horses diet and this is often over looked by riders and owners.

Traditionally grass and hay were the main sources of fibre in a horses diet but sources of fibre also include, haylage, straw, chaffs, alflalfa, sugar beet pulp. Obviously different horses and ponies have different needs and these need to be considered when looking at the animals diet.

Horse 5 of fibre in diet Type of fibre
Racehorse in training 40% Haylage/hay
Overweight/laminitic Up to 100% Chopped oat Straw/ soaked hay


For example a racehorse would have a diet high in compound feed (up to 80%) and low in fibre.  The fibre would normally be either seed hay or haylage and high in energy and protein.

However a native type which is over weight and needs to lose weight may be on a hay replacer like chopped oat straw with restricted grass turn out and a concentrated feed balancer.

Chopped oat straw is becoming a popular choice for overweight/laminitic type horses which need fibre to keep the gut healthy and the horse psychologically stimulated but needs very low calories (It is recommended that horses who have EMS have diets which are lower than 10% non-structural carbohydrate which is difficult to find consistently with hay so many people are now using chopped oat straw which is 2.2% NSC).


Not Getting Enough Fibre

Research is ongoing regarding equine nutrition but in recent years a diet low in fibre and high in starch has been linked to many diseases including laminitis, Equine Gastric Ulcer Syndrome, Polysaccharide Storage Myopathy (PSSM), Developmental Orthopaedic Disease (DOD), Equine Rhabdomyolysis Syndrome (ERS) and colic.  This highlights the important role of fibre in a horse’s diet.

The National Research Council committee on nutrient requirements of horses  stated that “The goal of feeding management is to efficiently supply dietary ingredients in amounts that will meet the horse’s nutrient needs, while still retaining the horse’s normal feeding behaviour” (NRC 2007).  The horse’s normal feeding behaviour is trickle feed fibre.


Grey horse eating hay

Horse eating hay

How much Fibre to Feed

Feed according to size, workload, temperature, and living conditions.  Most horses should consume between 1.5% to 2.5% of their bodyweight per day.  Overweight, or maintenance diets should be approx. 1.5% of BW, pregnant mares up to 8 months should be approx. 2% BW, while growing young stock and lactating mares can consume up to 2.5% BW, as a general  guide.  The total can be divided between forage and concentrates.  A horse in light work can have the diet 0-30% hard feed and 70-100% fibre when compared to a lactating mare on a ration of 40-60 hard feed and 40-60% fibre.  Every horse is unique so this is only a general guide.