Horses and ponies diagnosed with pituitary pars intermedia dysfunction and metabolic syndrome are prone to laminitis, a debilitating disease that can cause great physical pain and potentially loss of long-term soundness. Nutritional countermeasures may, however, keep susceptible horses from developing laminitis.
“Dietary management often focuses on restricting intake of nonstructural carbohydrates (NSC), namely sugars, starches, and fructans,” said Kathleen Crandell, Ph.D., a nutritionist with Kentucky Equine Research. “The consumption of these particular carbohydrates can increase the risk of laminitis through hyperinsulinemia or hindgut disturbances in laminitis-prone horses.”
Each horse or pony must be nourished in a way that best supplies its nutrient requirements while staving off laminitis. Here are some general points of consideration.
Diets should be based on appropriate forage, such as grass hay (or hay substitute) with a low NSC content (less than 10-12% dry matter) fed at a rate of approximately 1.5-2% body weight. Mature hay typically has lower digestible energy and NSC content when compared to less mature grass hay and legumes, such as alfalfa and clover. NSC content also depends on environmental factors during growth and harvesting. Whenever possible, a forage analysis should be performed on hay intended for horses with PPID and EMS. Soaking hay for 30-60 minutes before feeding is thought to leach sugars and fructans, and may be prudent in the absence of a forage analysis.
Restrict or avoid access to pasture. The NSC content of some forages can escalate to 40% dry matter at certain times of the year. Consumption of pasture can be controlled through the regular use of a well-fitted grazing muzzle; strip-grazing behind other horses or sheep; or mowing the pasture short and removing the clippings. Other grazing considerations include choosing a time of day when NSC are lowest in plants (late at night through early morning), avoiding spring or autumn grazing (before flower development or seeding), and steering clear of stressed grasses, such as those subjected to frost or drought. In situations that call for severe restriction of NSC intake, no grazing should be allowed, though an appropriate forage alternative can be fed in a drylot.
Feed a low-calorie balancer pellet or an appropriate vitamin and mineral supplement to horses and ponies on an all-forage diet. A balancer pellet usually contains a source of high-quality protein such as soybean meal. For aged horses or those with signs of muscle-wasting, a balancer pellet might be more appropriate than a vitamin and mineral supplement.
Avoid feedstuffs high in NSC, such as straight cereal grains (plain oats, for example) or sweet feeds. Sweet feeds that contain primarily cereal grains and molasses can boost the NSC content to 45-50%.
For lean horses or horses in work, other feedstuffs may be necessary for maintenance of weight. Concentrates low in starch and sugar content (15-25% NSC) when compared to traditional concentrates (30-50% NSC) may be appropriate in some instances. Energy is usually conferred by fat (vegetable oil, stabilized rice bran) and fermentable fiber (beet pulp, soy hulls) sources in these low-starch feeds. In other situations, unmolassed, soaked beet pulp or hay cubes with or without added vegetable oil can provide calories to horses at risk for laminitis.
Supplement with a rich source of omega-3 fatty acids, such as EO-3. In humans, omega-3 fatty acid supplementation is a therapeutic strategy used for metabolic dysfunction because it improves insulin sensitivity and reduces inflammation. A study in horses indicates that DHA alters circulating fatty acids, modulates metabolic parameters, and may reduce inflammation in horses with metabolic syndrome.*
Monitor body weight through regular weighing or body condition scoring. Attention to changes in weight or body condition score can keep horses in an acceptable weight range.
A nutritionist or veterinarian may suggest other management strategies based on the individual horse or pony and its risk factors for laminitis. Because there are many causes of laminitis, the disease is not completely preventable, regardless of vigilance.
*Elzinga, S.E., A. Betancourt, J.C. Stewart, M.H. Altman, V.D. Barker, M. Muholland, S. Bailey, and K. Brennan. 2019. Effects of docosahexaenoic acid-rich microalgae supplementation on metabolic and inflammatory parameters in horses with equine metabolic syndrome. Journal of Equine Veterinary Science 83:102811.