A disease caused by toxins produced by the bakterium Clostridium botulinum.

The bakteria occur in cadavers (the bodies of dead animals) and thrive in anaerobic conditions. Horses may ingest toxins produced by the bacteria through eating haylage or silage contaminated with a cadaver. 

Botulism toxins affect the nervous system. Typical clinical signs include progressive muscle weakness culminating in recumbency and difficulties swallowing and eating. Death may occur through paralysis of respiratory muscles. This is a very serious disease which is diffucult to treat.  Careful screening of forage before feeding is the best way of preventing its occurance.