If they are regularly coughing and the feed is not dusty then I
would take their temperatures as they may have a respiratory
infection and need antibiotics or they might have lung worms and
need drenching for worms.
I have no idea, but I have a suggestion. Guelph University, in
Canada, and Cornell University, in New York, work extensively with
goats. I would suggest contacting either, or both of them. One
should be able to answer the question you wanted to ask here, but
didn't.
You should know that goats are very hard to keep in. But if you
are up for the challenge, goats are great sources for milk, and
their milk is better than cows' milk.