breathing with it's beak open. Eyes are half closed and acts listless. Still eating and drinking. It first started coughing about 4 days ago. I set up a light bulb to give warmth but am at a loss as to what to do. Never had a sick chicken before. The bedding is pine shavings. Feed is a 'grower' mix of local manf. with no additives. Any help would be greatly appreciated.