Pigs fed a diet supplemented with selenium >20–50 ppm for >3 days develop a subchronic selenium toxicosis characterized by neurologic abnormalities. Animals are initially ataxic and uncoordinated, followed by anterior paresis, then quadriplegia. Even though neurologic impairment is occurring, the pigs continue to eat, which would indicate a non-centrally mediated neurologic damage. The hooves show breaks and impaired growth similar to those seen in cattle. Alopecia may also be observed. In sows, conception rate decreases and number of pigs born dead increases. Lesions of subchronic toxicosis include focal symmetric poliomyelomalacia, which is most prominent in the cervical and thoracic spinal cord. Death may result from complications of permanent paralysis. Hoof and hair damage is similar to but in most cases less severe than that observed in chronic selenium toxicosis. Treatment is similar to that for chronic toxicosis, but spinal lesions are usually permanent.

Last full review/revision March 2012 by Jeffery O. Hall, DVM, PhD, DABVT