Polioencephalomalacia in cattle is a neurological emergency caused by thiamine deficiency or sulphur toxicity, causing brain dysfunction, blindness, and severe suffering if untreated.
PEM causes one of the most acute and distressing neurological syndromes in cattle. Animals appear blind and disoriented, may fall and be unable to rise, and experience seizures — a terrifying and painful experience. Because the condition causes apparent blindness and disorientation, affected animals panic and injure themselves against fencing or equipment. The time window for effective treatment is narrow but the response to thiamine can be spectacular — animals that appeared moribund can recover normal behaviour within hours of appropriate treatment. Prevention through dietary sulphur management and monitoring, particularly in feedlot systems, is far preferable to treating established disease. Fast recognition and emergency thiamine injection are the most critical welfare interventions.