Naturally Occurring Selenosis in Wyoming

A review of Wyoming State Veterinary Laboratory records for 1947–1987 revealed no substantiated cases of naturally occurring selenosis. However, older reports attributed thousands of animal deaths to selenium each year in this area. Beginning in August 1988, cases of suspected selenosis and selenium deficiency were solicited from veterinarians and producers by announcements in various statewide livestock publications. As of August 1991, 4 cases (all horses) of naturally occurring selenosis have been confirmed. Clinical signs were most often referable to epithelial damage, e.g., hoof lesions and loss of mane and tail. None involved neurologic signs. Sources of selenium included native range and grass hay.