While pasture-associated laminitis is well known to horse owners, endocrine disorders, including hyperinsulinemia and pars pituitary intermedia dysfunction, are thought to be the most common cause of laminitis. A historical review of data from over 550 North American horses has identified risk factors for pasture- and endocrinopathy-associated laminitis (PEAL)*.
In the study, researchers identified 199 horses with PEAL and 351 other horses from two control populations (healthy horses  and horses with lameness not caused by laminitis ). Veterinarians involved in the study were asked to create case-control sets of three horses that consisted of one horse with PEAL and two control horses without laminitis. Veterinarians followed specific parameters in selecting horses for the study. Horses from 32 states in the U.S. and three provinces in Canada were included in the study.
The risk factors recognized in this study that increased the odds of horses developing PEAL included “obese body condition (i.e., body condition score of 7 or greater), generalized or regional adiposity (alone or in combination), preexisting endocrinopathy, or recent (within 30 days) glucocorticoid administration,” according to the research group. For those familiar with laminitis, especially endocrine-related laminitis, this group of risk factors likely seems familiar.
Avoiding laminitis in susceptible horses often requires owners to reassess management goals, foremost of which is a commitment to an appropriate diet and a suitable exercise program, if the horse is sound for work.
“Dietary changes may require a complete overhaul to eliminate excessive calories while still providing optimal nutrition,” said Catherine Whitehouse, M.S., a nutrition advisor at Kentucky Equine Research. “Examples of diet modifications include limited access to pasture either through restricted grazing or through the use of a grazing muzzle; removal of calorie-laden concentrates; and provision of a well-formulated vitamin and mineral supplement, such as Micro-Max (sold in the United States and other regions) and Gold Pellet, Nutrequin, or Perform (in Australia).”
Because horses are individuals and should be fed as such, consultation with a qualified equine nutrition advisor will ensure your horse is consuming the nutrients required for his well-being.
Exercise comes in all formsâ€”longeing, trail-riding, ponying from another horse, schooling figures in an arena, ground-driving, working at liberty, and countless other activities. “To help dodge the effects of endocrine dysfunction, researchers recommend at least 30 minutes of daily exercise, during which the horse’s heart rate becomes elevated for sustained periods,” Whitehouse said. (Check out KER ClockIt, a fitness app for horses.) Unfit horses should be gradually transitioned into a work program, and any question of soundness should be addressed with a veterinarian before a regular exercise program is implemented.
*Coleman, M.C., J.K. Belknap, S.C. Eades, H.L. Galantino-Homer, R.J. Hunt, R. J. Geor, M.E. McCue, C.W. McIlwraith, R.M. Moore, J.F. Peroni, H.G. Townsend, N.A. White, K.J. Cummings, R. Ivanek-Miojevic, and N.D. Cohen. 2018. Case-control study of risk factors for pasture- and endocrinopathy-associated laminitis in North American horse. Journal of the American Veterinary Medical AssociationÂ 253:470-478.