I have a hen that wheezes every time she breathes in and out. No discharge of the eyes or nose and no other accompanying symptoms other than maybe being slightly lethargic, although she keeps up with the others and eats/drinks just fine. It started when she became broody during the hottest days of summer - I tried to do some research and found that prolonged heat can mess up their respiratory system but there has been no real improvement and it actually seems more pronounced since the cold snap hit... Any suggestions??
Do you have any amoxicillin on hand? 250 mg gelcap once a day for two days will usually kick any respiratory issue. Dip it in water before you slip it down the throat..it slides better. You can get Amoxicillin 250 as fishmox at Walmart or many of the feed stores...runs about $20 for a bottle of 50 pills. That's a lot cheaper than getting 12 pills for $20 from the vet.
As your next line of defense, Gallimycin or Denegard mixed in drinking water. I keep both on hand. Gallimycin is a powder and Denegard is a liquid.