I hope you didn't see a dosage for a medication that is prescription only recommended on this site. It's illegal for any of us to recommend and dose a medicine without a veterinary license. Additionally, I wouldn't recommend doxycycline for a respiratory infection without discussing it with a qualified veterinarian. It's a strong anti-biotic that frequently causes GI upset (my chin got immediate liquid diarrhea after just one dose) as well as other side effects. IMO, a safer option would be Trimethoprim-Sulfa, aka Bactrim, aka Sulfatrim, but you must get this from your vet.
