Join Date: Feb 2012
Location: Washington state
You didn't give much detail so it's hard to say anything.
The thing is with horses, something like a cough can be anything from dust to death. That panics most of us right off our rockers. Are the horses running fevers? Are there any other symptoms? How long have they had it, how deep or shallow is it. Is the feed dusty? Could they have a cold? There are about a million things it could be and without more information it's impossible to even speculate.