I don't know if this will be of any help to you, but I had a situation last spring when my chickens had rattly respirations. I started by giving my ionic silver in their water (natural antibiotic), then treated the worst ones for gapeworm using fenbendazole. That did not result in improvement, and others started making the gurgly, rattly sounds as well. They had no other symptoms, no runny nose, eyes, and were acting normal.Then my Ameraucana hen became "croupy" - I could hear her breathing from outside the chicken coop.
In the end, I concluded that this was not a gapeworm issue after all. When my Ameraucana hen developed the loud, croupy sound I did some quick searching to find out what I could give her in terms of a natural bronchodilator. I learned that there are various things that could relax the airway: licorice, cayenne pepper, bromelain, coffee, magnesium, anise seed oil, and ACV would help also, I read. I made a mixture of whatever I had available, and gave the croupy hen a few mls. She took it well from the syringe (by mouth). Twenty min later she was still making the croupy breathing sounds, very loud noise on breathing in, no other symptoms. I then decided to give the mixture to another hen as well, as she was rattly. As I was doing that, I suddenly realized that the noise from the Ameraucana hen had stopped. Her breathing was quiet. I came back later and she was making only the occasional slight noise, and the other hen was no longer gurgly. So, I concluded that they had something that was affecting their airways, and it seemed the natural bronchodilators helped (my theory). I then treated all of the rattly gurgly chickens with the same mixture and they all were breathing normally within 30 min. I repeated the treatment a few times the next morning and evening for a few when I heard the noises, and each time, they settled to normal breathing. The next day they were all back to normal. No medications needed, didn't have to discard any eggs, and the symptoms did not recur.
