Why horses should be fed a fiber based diet.
Horses are non-ruminant herbivores (non-ruminant means they do not have multi compartment stomachs like cattle).
There nutrient requirements are derived from a diet of plant material. This is made up of mainly fibrous plants like grasses which contain soluble and insoluble carbohydrates in varying amounts. The horses digestive system is unique in the way it digests food...
Food is first ground with the teeth and mixed with saliva in the mouth. Saliva is needed to regulate the acidity of the stomach, as fiber takes more chewing, more saliva is produced. (Lack of fiber has been linked to gastric ulcers). Food then enters the stomach where it is mixed with digestive juices pepsin (an enzyme to digest proteins) and hydrochloric acid to assist break down of solid particles. It then moves into the small intestine where most soluble carbohydrates are absorbed, along with vitamins, minerals, fats and proteins.
Overtime horses digestive systems have evolved a digestive tract with an enlarged pouch called a cecum (which is a microbial fermentation vat). It is the horses close association with hundreds of microorganisms that produce the enzymes able to break down the insoluble carbohydrates, making the food available to both bug and horse. When this fibre is broken down by the microbial organisms, they release volatile fatty acids, which when absorbed provide immediate energy for the horse. They also produce some vitamins such as K and B complex, microbial proteins, digestive enzymes and carbon dioxide.
It is important to provide ample fibre to keep the microbial population healthy. Any sudden change in diet can have adverse effects on the bacteria population taking up to three weeks for the microbial population in the cecum to return to normal. Other factors that can compromise the micro flora are stress,[click stress for information why being stressed too often and for too long will effect both horse and hoof health ] overheating, antibiotics, chemical wormer and other medications.
Example. Soluble carbohydrates from too much grain or lush grass leaking undigested into the cecum causes a population explosion of the bug Lactobacillus. When digesting these soluble carbohydrates they excrete lactic acid; more and more bacteria multiply which produce more lactic acid causing the pH in the environment to drop. It becomes more acidic causing a die off of other bacteria who cannot tolerate the drop in pH. By dying they release toxins which are absorbed into the bloodstream which can cause laminitis.
So treat the hind gut with respect and feed your horse as naturally as possible, by doing this you will greatly reduce the risk of laminitis, colic, and other gastrointestinal tract problems.