Glucose intolerance/insulin resistance and problems with carbohydrate metabolism are being diagnosed with increasing frequency
in horses. As veterinary knowledge and scientific understanding of these conditions increase, more horses may yet be included
in this large category. The guiding principle for feeding these horses is to lower the amount of soluble carbohydrate and
increase the fat and fiber. The feeds being produced for these horses try to control starch and sugar and often contain higher
levels of certain vitamins and minerals that have been shown to increase and optimize metabolism, such as vitamin E, zinc,
chromium and magnesium. The research into feeds for these conditions has been so aggressive that some low-sugar/low-starch
feeds have been formulated to have less carbohydrate content than even a diet of simply hay. Horses diagnosed with equine
Cushing's disease, glucose intolerance/insulin resistance or other types of carbohydrate metabolism problems, as well as horses
suffering from laminitis, even if not affected with other underlying disease(s), can benefit from a these diets.
Veterinarians long have been treating horses with chronic obstructive pulmonary disease (COPD) with dietary management since
"heaves" often can be influenced and affected by intake of dust, mold and any number of other allergens. Some of these allergy-inducing
particles undoubtedly are taken in through the digestive tract. Because hay is a prime source of dust and mold in the diet
of a horse, many of the feeds that have been produced to treat equine allergies are "complete" feeds that have a beet-pulp
base as a highly digestible fiber supply. This addition to a horse's fiber intake allows owners to all but eliminate the feeding
of hay or to use hay cubes, chopped forage or chaff products, which are much less prone to contain allergens.
Most practitioners and nutritional researchers agree that many cases of equine colic are related to nutritional mismanagement.
Studies have shown that overloading the small intestine with carbohydrates reduces that section of the intestine's ability
to correctly process feed, which leads to increased fermentation of starch in the cecum and colon. This tends to cause bacterial
overgrowth, increased gas production and often leads to colic. Diets that are lower in soluble carbohydrates and that are
highly digestible (pellets vs. whole grain) may be used with susceptible horses to reduce the risk of intestinal upset.
The clinical signs of equine polysaccharide storage myopathy (EPSM) or (PSSM) can be varied, and many horses exhibit these
sometimes subtle gait alterations. Effected horses can show loss of muscle mass through the shoulders or hips. Abnormalities
seen when flexing the stifle, such as shivers, stringhalt and patella fixation, all can be associated with cases of EPSM.
Horses with this condition can show only excessive sweating with exercise or weakness and muscle trembling and difficulty
when backing or turning. Some horses might be reluctant to have their feet picked up to be cleaned or trimmed and might stamp
their feet or be reluctant to hold themselves on one leg for very long. It is thought that these horses suffer from a defect
in glycogen synthesis regulation that makes them unable to metabolize starches and sugars properly. This defect results in
levels of glycogen in the muscles of these horses that can be 1.5 times to 4 times higher than normal. The increased glycogen
uptake in the muscle of these horses has been linked to an abnormally high insulin response. Though many facets of this response
have been uncovered, there are more aspects that remain unknown. Nutritional treatment can be rewarding in some of these cases
with the suggested diet attempting to reduce starches and sugars drastically. Fiber content is maximized for these horses
and between 20 to 25 percent of the caloric requirements is provided by easily digestible fat. Higher fat requires increased
vitamin and mineral levels, especially vitamin E, and most of the designed specialty diets reflect this need. These horses
also should be restricted from access to lush pasture as exposure to fructan, a carbohydrate found in green grass following
certain environmental conditions, can worsen EPSM. The use of dried forage substitutes or hay cubes can be beneficial in the
management of these cases.