I was happy to hear you have German Shepherds that guard your chickens. We have a corgi and older border collie that do great here keeping the riff-raff away, but our next dog I want to be a GS.
As for sexing your chickens, @Jener8or gave you the link above. Since your silkies are a mix, they may be able to be sexed sooner than usual. Otherwise, it's mostly a guessing game until they crow or lay an egg.