Chapter 16 - Pasture-Related Diseases and Disorders

Abstract

Maximizing intake of pasture, minimizing grain intake, offering good quality hay when pasture supply is low, providing plenty of good quality water, and preventing horses from eating on sandy surfaces can all help to reduce the incidence of colic in grazing horses. Testing forages for nonstructural carbohydrate (NSC) levels and feeding only low NSC pasture when possible will help to reduce the probability of horses becoming obese and developing associated laminitis. Use of oral glucose tests, restricting access to pasture, and use of grazing muzzles can also help to prevent pasture-associated laminitis in susceptible horses. Obstructive pulmonary diseases can be prevented by ensuring that forages for susceptible horses are very low in mold and dust content, keeping pastures short and leafy, carefully choosing appropriate forage species, and removing susceptible horses from pasture. Toxic plants found on pastures can include trees, forbs, legumes, and grasses, some of which may be infected with fungi. Prevention of poisoning of horses on pasture includes rotational grazing with enough paddocks, sufficient area per horse, short grazing periods, long rest periods, learning to identify toxic plants, and removing or blocking access of horses to toxic plants. Restricting amounts of nitrate from fertilizer, manure, or other sources that can enter and accumulate in pasture plants, especially after a frost, can help to prevent nitrate and nitrite poisoning. Learning the typical concentration of selenium in your soil and pasture plants can help horse managers decide whether supplemental selenium is required. In areas with alkaline soils and dry climates, recognition of selenium-accumulating plants and preventing their consumption can help to avoid selenium toxicity. When abnormal signs are observed in a horse, following a change in location or diet, especially if a recognizable toxic plant is found where the horse is grazing, and calling the ASPCA Animal Poison Control hotline at (888) 426-4435 can help with diagnosis of the problem and provide useful information regarding veterinary intervention.