When several horses develop botulism, toxin in feed or water is usually the reason. Since large wrapped round bale haylage came into common use, there have been several reports of groups of horses developing botulism after eating this type of feed. It was first reported in Great Britain but it has occurred in Canada too. In some of these outbreaks, the haylage looked and smelled spoiled. In others, the bales didn't look as if they were spoiled but horses eating them developed botulism.
Botulism is difficult to treat.
It is most beneficial if used when animals are first seen to be sick. With supportive care, horses can recover but, if they are exposed to a large amount of toxin, most will die despite treatment. There is a vaccine available in Canada to protect horses against botulism. This information is provided as a public service, but we cannot guarantee that the information is current or accurate. Readers should verify the information before acting on it.