The importance of forage (pasture and/or hay) is underscored in every primer on horse nutrition. Forage is chock full of fibre, a dietary component that is subjected to microbial fermentation in the caecum and colon of the horse. This fermentative process produces volatile fatty acids, important sources of energy for horses fed high-forage diets. Fibre can supply a horse with 30-70% of its digestible energy requirements.
What are 'super fibres'?
While forages are well-known sources of fibre, other feedstuffs are considered 'super fibres' because they have energy levels much higher than typical forages. The energy levels in super fibres are slightly less than those found in cereal grains such as oats and barley. Super fibres are, however, safer to feed than cereal grains because their fibrous nature reduces the likelihood of grain overload.
Types of 'super fibres'
The most commonly fed super fibres in the United States are beet pulp and soy hulls. These feeds are more digestible than traditional fibre sources. For instance, hay is 40-60% digestible, depending on its quality, and beet pulp and soy hulls are 80% and 75% digestible, respectively.
In Australia, lupins are becoming a popular ingredient in rations. Lupins increase the energy density of a ration, due in part to their highly digestible fibre content. Other advantages of lupins include exceptional palatability and low cost.
Sugar beet pulp is a by-product of the sugar beet industry. After the sugar has been extracted from sugar beets, the fibrous portion of the sugar beet is dehydrated. Dried beet pulp is often used as an ingredient in textured feeds by feed manufacturers, or it can be added by the handful to a premixed concentrate to boost the fibre content of a ration.
Differences of opinion abound as to whether beet pulp should be soaked in water prior to being fed. Some horsemen believe it is an absolute necessity. Others have never bothered with wetting beet pulp and have not encountered any problems. When a horse is reluctant to drink, offering soaked beet pulp is one way of encouraging a horse to ingest water.
The seed coats of soybean seeds are called hulls. The hulls are very much like the thin, skin-like structure that surrounds peas. Soy hulls are quite different than pods, and the two must not be confused.
Pods are typically left in the field following combining. Hulls are usually separated from the soybean during oil extraction. Following separation, the hulls can be toasted, ground, and blended with soybean meal to lower the crude protein content of the meal. Soy hulls are low in lignin (indigestible fibre) and are therefore more digestible than hulls from other grains or seeds.
Less popular than beet pulp and soybean meal, almond hulls are another super fibre. Although they are used predominantly in cattle feeds (both dairy and beef), almond hulls can have a place in horse rations. Before dehydration, almond hulls are similar in texture to the edible fleshy portion of a peach that surrounds the stone. Once dried, almond hulls are as fibrous as high-quality grass hay.
Benefits of feeding 'super fibres'
Horsemen feed super fibres for a variety of reasons. Some horses will not or cannot eat large enough quantities of hay to fulfill fibre requirements. Dental problems, for example, may keep aged horses from consuming sufficient hay or pasture. Caretakers should offer fibre in other forms.
Horses on diets composed largely of concentrates (grains) may be unwilling to eat large amounts of hay. In these instances, fibre can be introduced into the concentrate as beet pulp or soybean hulls. Due to their high energy content, super fibres are also ideal for horses that have difficulty maintaining weight.
Some performance horses also benefit from super fibres, especially those asked to perform at moderate speeds for long distances such as endurance horses. In addition to being a steady energy source for horses, super fibres help maintain intestinal health. Consumption of fibre can increase water intake, creating a holding tank of water and electrolytes in the hindgut. This reservoir may prevent dehydration and electrolyte depletion during an exercise bout. Endurance horses, for instance, have only limited time to eat during a ride. An appetising, fibre-rich meal, such as a slurry made of beet pulp, wheat bran, and grain, can supply the horse with sufficient energy and water to remain competitive.
Horses that do not tolerate diets high in starch may also benefit from super fibres. Horses afflicted with recurrent exertional rhabdomyolysis (RER) or equine polysaccharide storage myopathy (EPSM) often find relief when fed diets low in starch. When super fibres are fed to these horses, much of the energy necessary to support exercise is derived from fibre and not starch.
Augmenting the diets of horses with super fibres will increase the energy content of rations. An added boon to the use of super fibres is the positive effects they have on preserving gastrointestinal health.