- Jul 26, 2010
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The white powder is mold. It makes horses sick. Shaking it out or washing the hay still leaves a lot inside the stems and leaves of the hay. Sometimes the horses eat it for a little while and don't get sick. If they are getting enough mold, they'll get sick. It doesn't take much. And where mold grows, bacteria grows, too. So diseases like botulism are also possible.