Apple cider vinegar is useful in many ways. It is a good source of potassium and is quickly absorbed. Potassium is important to build strength and fight bacteria by flushing out toxins. It boosts a chicken's respiratory, immune and digestive systems and helps with calcium absorption. Also, it helps fight and prevent cancer, infections, diseases and illnesses. ACV is high in vitamins, electrolytes, probiotics and minerals. It also is thought to be a mild antibiotic. If you are going to be moving your chickens to new housing, introducing to the flock or if your birds are molting make sure to use ACV as it helps reduce stress levels.
Apple cider vinegar is most commonly used in the water. (1 tablespoon per gallon.) This vinegar will fight off bacteria growth in the waterer itself. Note: Never use ACV in metal water containers as it will break it down and leach harmful chemicals into the chickens' drinking water. Some people even claim that their chickens prefer the taste of water with ACV instead of plain water! ACV can also be used in a bath for your chickens. ACV will kill and rid your chickens of any external parasites. Plus it conditions the skin. You can use ACV for cleaning nest boxes, feeders, waterers and incubators too.
Overall, I love using ACV with my birds and believe it is extremely healthy for them.