My Brown Leghorn Rooster (very pretty boy) is very sick. I found him this morning with his head down and his comb on the ground. His comb is turning blue, I guess due to lack of oxygen. I have checked his to make sure he has nothing stuck in his mouth, but there is nothing visible blocking his air ways. He was fine yesterday, so I have no idea what happened to him. There are no visible abrasions or other signs of trama.
Have you listened to him breathing...you don't need a stethescope, just put your ear up to his side. It should sound like a bellows with no squeaks, rattles or crackles. You can put VetRx in the water and Vicks Vaporub near his nostrils and under his wings.
The very first thing you should do is to take him to the vet to see if there may be an infection somewhere.
I too suggest taking him to the vet...the blue comb indicates cyanosis / lack of oxygen (due to heart insufficiency) however is this is due to disease or something toxic he may have eaten I have no clue as there simply is not enough info here...