Why would you need to? Goats are much cleaner animals than sheep, and if they do soil their backends (after a few ash branches too many it can happen quite quickly) a wash with warm water and shampoo will sort it - I have never heard of flystrike in goats!
Also if you are milking them it would be unlikely that you could use CRovect on them.
If they are bothered by flies in certain weather conditions a natural fly repellent (probably available for horses) should sort it.