ACV is great for health- people and chickens, but is not useful for preventing or treating worms other than it promotes a healthy GI tract. I suppose it might help the chicken better tolerate the worms that it has....
I have heard that if you put cider vinegar into your water feeder it keeps your chickens from getting worms !!!!
You dont have to add much -just a couple of tablespoons to a gallon or so of water. Its cheap to buy and use-
God knows vinegar has many uses!!!
I use cider vinegar in their water daily for its great qualities such as helping the chickens system properly absorb calcium and keeping PH in balance. However, I can assure you that cider vinegar doesnt keep your chickens from getting worms.