Benefits of a High Fibre, Low Starch Diet for Horses
Horses are trickle feeding herbivores that have evolved to consume a diet rich in structural carbohydrates (fibre), but low in soluble polysaccharides (starch).
Fibre sources such as hay, haylage and grass are vital for a healthy digestive system and should always form the majority of the diet. Fibre also provides the horse with excellent levels of slow release energy and a good source of calories and heat as it is fermented in the body.
Starch is a carbohydrate found in cereal grains such as barley, maize and oats and provides a good source of fast release energy.
While starch is not ‘bad’ as such for the horse in small quantities, it can cause problems if the horse eats too much in one meal.
It is well documented that horses are ineffective at utilising starch if fed in excess and recent studies have concluded that horses should be fed a low starch diet, as higher amounts can lead to the development of gastric ulcers, insulin resistance, laminitis and muscle myopathies (such as tying up).
It is essential that horses are fed according to their individual needs. Horses at maintenance should be fed high fibre, low calorie feeds to avoid excess energy being consumed. However, horses that are in work and require more energy, do not necessarily need to be fed concentrated meals, high in starch, to get the extra calories needed. Highly digestible fibre, combined with oil, can provide a good level of calories in a form that is more suited to the digestive physiology of the horse. Ensuring that all horses, whatever their individual needs, are correctly fed is essential for health; common areas for consideration are listed here:
Horses in Work
Performance horses or working horses will generally need to eat more calories to provide the energy they require. Once again, basing their diet on the NRC (2007) principle of energy provision, diets can be tailored according to weight, body condition score (BCS), workload and temperament. As mentioned previously, horses requiring higher energy levels do not necessarily need to be fed feeds high in starch, as high fibre, high oil diets can provide the energy needed.
Horses at Maintenance
Horses and ponies that are classed to be at maintenance, need to be fed a diet high in fibre, with the right level of calories (depending on if they are a good or poor doer). The diet also needs to ensure good protein sources are provided along with the right balance of vitamins and minerals. As with all horses, those at maintenance should be fed according to the level of work they are in, to meet their individual energy requirements, the simplest system being that set out by the National Research Council (2007).
The NRC (2007) system bases the amount to be fed on the daily digestible energy needs of the animal. By ensuring correct energy levels are provided, horses and ponies that are prone to becoming either under or overweight can be managed effectively.
Horses and ponies that have undergone surgery, may have compromised digestive function; this will definitely be the case if the animal has had colic surgery of any sort. Diets for post-operative animals, therefore, should provide highly digestible fibre, as well as good sources of protein and vitamins and minerals.
Feeds containing both prebiotics (such as fructo-oligosaccharides (FOS) or mannan-oligosaccharides (MOS) and probiotics (live yeast), can be beneficial as they help to support digestive capacity by improving the microbial population within the gut.
Insulin Resistant Horses
Horses and ponies suffering from insulin resistance (IR), hyperinsulinaemia or diabetes should be fed a diet low in both starch and soluble sugar. Ensuring the diet does not provide more than 10% combined sugar and starch is essential for managing the glycaemic response and therefore the insulin peak. Several studies have suggested that certain ingredients may increase insulin sensitivity (SI) in these animals. However, other ingredients such as cinnamon, beetroot, soy isoflavones and FOS have all been found to have beneficial effects on animals, including horses, so are sometimes given to those suffering, although more work needs to be carried out in this area.
Laminitis can be caused by varying factors, however, dietary and metabolic causes of the disease can be managed successfully by appropriate feeding. As with IR horses, animals with, or prone to laminitis must not be fed a diet containing more than 10% starch and sugar combined and starch should also not be fed in greater amounts than 1g/kg Bodyweight (BW)/meal. Care should also be taken when advising on suitable forage types, as even soaking hay may not remove all the soluble sugars from the plant. High fibre, low starch feeds should be fed with adequate levels of protein and vitamins and minerals. If the horse is overweight, the amount of feed given may need to be modified to ensure weight loss is achieved.
Horses and ponies that are overweight are susceptible to many health problems, not least laminitis. Research conducted by Dr Argo at the University of Liverpool – School of Veterinary Science, found that by reducing the amount fed to just 1% of BW may be necessary to produce weight loss. Such a drastic reduction in feed should be monitored closely under veterinary consultation to ensure the horse does not develop other health problems.
Conditions such as polysaccharide storage myopathy (PSSM) and Equine Rhabdomyolysis Syndrome (ERS) also need careful management of the soluble carbohydrate intake and feeds high in fibre and low in starch must be fed. The overall diet should not contain more than 12-15% starch and no more than 1g starch/kg BW/meal must be fed.
Liver and Kidney Problems
In cases of renal dysfunction, horses should be fed a diet which is low in protein (less than 8%) and low in calcium and phosphorus. Feed ingredients such as alfalfa should be avoided as they are high in both protein and calcium.
If the animal is suffering with liver dysfunction, then once again, a diet low in protein, but also low in oil (less than 4%) is needed. In addition, high-fat diets must be avoided and feeds high in starch and sugar may be needed to ensure adequate glucose metabolism.
Not all veteran horses need a specialist diet, however, as the body ages, just as in humans, there is a general deterioration in physical well-being. Degenerative problems such as failing dentition and decreased digestive efficiency will need careful management. A diet that delivers a good source of available protein, as well as providing high amounts of fibre and low levels of starch is therefore often necessary. For older horses with poor teeth that struggle to chew long fibre, feeding a high fibre feed that can be soaked is ideal and will ensure the horse consumes adequate amounts of nutrients. For more information on feeding an older horse, please click here.