Why we love fibre
By Katie Williams M.Sc. (Dist) B.Sc. (Hons)
The horse is an herbivore and has evolved to spend long periods of time eating vegetation that has a relatively low nutritional value. If the balance changes with either the time spent eating reduced or the feeds eaten being high in nutritional value, problems can occur. Research has shown that there are many ways in which moving away from a high fibre diet can affect the horse which include diseases and behavioural problems.
Most horses and ponies get some time at grass and for many it makes a significant contribution to their nutritional requirements. The relatively high energy level of improved pastures can result in weight gain in good doers given unlimited access. Improved pastures also tend to contain a higher proportion of rye grass which has much higher levels of fructan (the sugar linked to laminitis) than grasses such as Timothy. If access to grass has to be restricted then alternatives have to be used to ensure that sufficient fibre is provided to maintain the health of the digestive system.
The Importance of Fibre
Unlike humans, the horse only produces saliva when he is actually chewing food not in anticipation of eating or if he can smell something he likes. Saliva is very important as it contains bicarbonate which helps to neutralise the acid produced in the stomach. The more time the horse spends chewing the more saliva he produces and the more efficiently the stomach contents are neutralised. If the horse spends less time chewing it increases the risk of gastric ulcers as the stomach contents are more acidic and so damage the stomach lining.
Fibre is fermented in the hind gut which is made up of the caecum (pronounced seek-um) and large intestine. A population of micro organisms is responsible for digesting fibre as the horse, like other mammals, isn’t able to produce the enzymes needed to break down fibre itself. As the micro organisms break the fibre down they produce volatile fatty acids (VFAs) which the horse can utilise as an energy source. On a high fibre diet the VFAs produced are weaker acids and so the gut is kept within an acceptable range of acidity. When starch from cereals reaches the hind gut it produces very strong acids which can make the gut too acidic for many micro organisms to tolerate and that is when problems such as colic and laminitis can occur.
The fermentation process also generates B vitamins. A healthy horse receiving plenty of fibre should be able to produce sufficient B vitamins to meet their requirements which is why B vitamins are only usually added to feeds and supplements intended for horses and ponies that may be receiving very little fibre in their diet or for individuals that may have reduced fibre digestion capabilities.
Another important by-product of fibre digestion is heat which is literally the horse's own central heating system. This is one reason why in colder conditions it is vital to feed plenty of fibre so that your horse can keep itself warm. In hot conditions horses may reduce their fibre consumption in order to regulate their body temperature. This can lead to problems as, just as for humans, fibre is very important for maintaining regular gut and bowel movements. Peristalsis is the process of the muscles of the digestive tract contracting and relaxing to literally squeeze food along. Too little fibre can result in very loose droppings and may also allow gas to build up eventually resulting in colic symptoms.
The Effect of Fibre on Behaviour
As the horse would naturally spend a long time eating, reducing the amount of food available to him means that he spends much longer doing other things. It was thought that boredom lead to the onset of stereotypies or stable vices but it is clear that the contributing factors are more complex. For cribbing or windsucking there may well be a link to increased acidity in the stomach due to reduced saliva production which is why feeding antacids seems to help some horses. Other stereotypies such as weaving and box walking are probably linked to separation anxiety and a response to the stress of being confined to the stable. There is also likely to be a 'genetic' element which would account for why horses on the same diet and managed in the same way aren’t all affected.
Although returning the horse to a more natural existence would probably help to reduce the risk of stereotypies occurring, it isn’t always practical to do so. Feeding plenty of, if not ad lib, fibre is the first step to trying to counteract the negative effects of domestication. In some cases cereal based feeds are required but for many horses and ponies, a fibre only diet would easily meet their energy requirements and should be considered to be of fundamental importance to a horse’s welfare.
A Fibre Revolution
As research conducted in recent years suggests that many diseases including laminitis, colic, gastric ulcers, Developmental Orthopaedic Disease (DOD), Equine Rhabdomyolysis Sydrome (ERS) and Polysaccharide Storage Myopathy (PSSM) are linked to high starch diets, it is no surprise to us at Dengie that a fibre revolution has begun! To be part of that fibre revolution find out how to convert your horse to a high fibre diet.