Investigation of Selenium Sources Associated with Chronic Selenosis in Horses of Western Iowa

In a 1993 study, chronic selenosis was diagnosed in horses in western Iowa, an area not previously known for seleniferous crops. The condition was linked to locally produced alfalfa hay with elevated selenium levels, likely due to drought conditions that allowed alfalfa roots to access selenium-rich subsoils. Affected horses exhibited symptoms such as moderate to severe tail and mane alopecia, hoof deformities, and lameness. The study involved 12 horses across two sites, with all recovering after switching to lower selenium hay. Historical data from 1983 indicated similar issues during a previous drought. Selenium concentrations in various samples were measured, confirming elevated levels.