I have used it in the past, but my chooks have been under pen arrest for such a long time (weather related!) and with the ducks, that I'm giving them flubinvet this time - it's a scutter though - mix the measured amount in with a little food, then mix that in with more, then in with the whole amount, and every day for a week - last day tomorrow thank goodness! No worms seen at any time but better safe etc.