Equine botulism occurs when horses are exposed to botulinum neurotoxin, an incredibly powerful toxin produced by the bacteria Clostridium botulinum. The most common way a horse becomes exposed to this toxin is by eating feed that has been contaminated with bacterial spores and subsequently having conditions that allowed for growth of those bacteria and release of the toxin. Clostridium botulinum spores can be found in soil almost anywhere, making contamination with these spores extremely common. High risk feeds for equine botulism include haylage, silage, and round bales. Any feed, however, can become contaminated and reports of equine botulism caused by square bales, pelleted feeds, sweet feeds, and even pasture clippings have been received.
