Atypical myopathy (seasonal pasture myopathy)
Atypical myopathy (also known as seasonal pasture myopathy) is an acute, non-exertional, often fatal disease in which large quantities of muscle cells break down. Horses at pasture of any age can be affected, but young horses on sparse pastures are particularly at risk, as they are thought to consume larger quantities of sycamore seeds and their toxic substance, hypoglycin A. The disease occurs more frequently in autumn. In addition to removing sycamore trees, their seeds, and plant parts, horses on grazed-down pastures should be given sufficient supplementary roughage. An adequate supply of vitamin E and selenium is also recommended.