If you change your mind about the Tylosin you can purchase it without a prescription in powder form
https://birdpalproducts.com/products/tylosin-powder-for-birds?_pos=1&_sid=2b1e7ad05&_ss=r
You‘ll need 12 ml syringes to administer it orally. Don’t bother mixing it in their water, it’s extremely bitter and they won’t drink it.
Dosage is 40 mg per kg, twice daily.
Dosage can be as low as 10mg per kg but from my personal experience it isn’t effective in geese at a dosage lower than 40mg per kg twice daily.
If you don’t have a gram scale to measure it exactly I can show you how much to put in a syringe if need be.
Baytril is something else you could try
https://birdpalproducts.com/products/enrofloxacin-10-liquid-for-birds?_pos=1&_sid=df4d5cc8c&_ss=r
Dosage is 0.05 ml per pound.
If your birds do have a fungal infection antibiotics should not be used unless absolutely necessary as they can worsen the infection. However it is difficult and costly to confirm. Asper can be sneaky and mimic symptoms of various diseases for awhile which makes it easy to mistake for another illness, but on the other hand from my own experience because of that it can easily become the “boogie man” of avian diseases, where everything appears to be asper.
High pitched coughs in my geese are usually a result of a secondary lower respiratory effect from an intestinal illness or a bacterial upper respiratory infection.
My gander Thor had confirmed asper and passed away from heart failure as a result of side effects of itraconazole. He had a high pitched cough but it had a weird pitch. His normal voice had also altered and had strange muted nasally pitch to it. Before that his symptoms were extremely non specific, his appetite wasn’t great, he wasn’t interested in eating, he was subdued and not really enthusiastic or excitable about anything, besides that there wasn’t anything that stood out.