This is correct,but i always keep a supply of Amprolium and Tetracycline in my first aid kit,in the event that any of my chickens were ill with a respiratory like issue and i could not reach my vet,they get Tetracycline.I have been doing a lot of reading and have seen repeated warnings against giving meds until you know what you are dealing with as they can interfere with diagnosis, cause super germs, etc or just mask symptoms. So I have given vitamins, lots of good scraps etc, probiotics. But I am still trying to get a diagnosis.