What symptoms are you seeing in your chickens? Oxytetracycline or LA200 is an injectable drug for cattle to be used every 3 days. It is not meant to give it orally to chickens, and you should never treat birds who do not show symptoms. It would only treat MG, but not viruses that cause respiratory diseases. You would be better off separating your sick chickens, and medicating with Tylosin powder in the water if you think that they have symptoms of MG. It is available here and dosage is 1 tsp per gallon of water for 3-5 days:Can you tell me how much to put in their drinking water to treat chickens? We have over 200 birds.
If you start a new thread of your own, you will probably get more responses.