Sick rooster what to do

[Emma_Bruffy]

So my RIR rooster Dan is not doing so good. Yesterday I noticed he was falling asleep standing up (I will post vid that I took yesterday) and I thought maybe something spooked him the other night and he didn't get much rest. Well that theory faded, today he was full on laying down "sleeping". I separated him and examined him he is not gasping for breath, sneezing, or coughing but I put my finger in his mouth and there is a opaque mucussy like substance in his throat.

 

[Emma_Bruffy]

 

[Emma_Bruffy]

And another thing is animal antibiotics aren't on shelves anymore so how would I go about treating him.