Note: My original post was a question about reducing dosages for chicks as opposed to adult birds. I found information through multiple searches - and wanted to document my procedures in case someone else could find the notes helpful. Symptoms from my birds: I think my birds have respiratory infections. Two of them (out of seven) have wet-sounding breathing - when picked up, they become excitable (normal) and their breathing sounds raspy/rattly and labored. They are sneezing a couple times every few minutes and have no nasal discharge. Birds all appear to be eating and drinking normally. Aside from the breathing noises, they are behaving as they normally do. They are on MannaPro Chick Starter medicated feed and water with electrolytes and ACV (filtered, pasteurized). My initial reaction was to house the sick birds separately, but since all the birds would still be in the same room, all the birds already had what would have been several days' worth of exposure to the sick birds, and I did not have extra brooder equipment, I ended up keeping them all together (not to mention when I separated the two birds out, one of them just chirped non-stop for it's buddies). Observations and flock detail: RooRidgeFarm's advice on anti-biotics in another post are my unofficial guide for this bird care adventure. Based on my initial observations over the past couple days and right now, I decided on using Tylan to treat them. I think they have a viral respiratory infection, but I am not a veterinarian, so that's just my best guess on observations. Though the virus won't be affected by Tylan, I am administering it to the birds who sound the worst (sneezing and wet, raspy breathing while under duress - i.e. being held by the scary humans) due to worry about secondary bacterial infections. Out of our 7 birds, two are showing obvious symptoms while two others have somewhat raspy/rattly breathing when held against my ear. One bird is about 2.5 weeks old while the other is a week younger. We are first time chicken owners, buying from two semi-local sellers on Craigslist. We did not quarantine our second set of birds, even though I knew that I should have as the best practice, due to the fact that I was too cheap to go spend another $35 on a second set of equipment. All our birds are on water mixed with electrolytes and ACV unfiltered, unpasteurized ACV and I feed MannaPro Chick Starter Medicated. The brooder floor is sand. The water bottle gets emptied, washed, and refilled daily. Brooder temperature is a constant 90° under the heat lamp. A digital scale for daily weighing would help me more than making occasional observations and assuming that everyone is eating and drinking normally. Process: 100ml Tylan 50 was $16 at a local veterinarian supply shop (unrefrigerated w/ cattle medication). I was not able to find 100ml Tylan 200 there, at the local co-op, or at TSC (which had 250ml for $32). Walgreens sells 10-packs of 29-ga, 1cc syringes for ~$3.40. Total cost for treating these two birds is ~$20. Treatment is .10ml per bird (1ml=1cc) given subcutaneously* twice per day injected on one side of the breast, alternating for each shot. I angle the needle away from the breastbone and try to just barely puncture the skin. *Due to my lack of skill and their small size, this has varied between subcutaneously and intermuscularly. Journal: Day 1 - I'll pull .2cc before administering injections (both birds use the same needle). I make sure to pull a little extra if I can't get rid of the air bubble completely (most the time I can). If I have an air bubble in the syringe, I pull another .02cc and flick the syringe when I have it held needle down to get the air bubble to a safe position. Round 1 3:45pm - both birds were pretty unhappy about the shot. I tried to keep the needle shallow and imagine a cooked bird when I was positioning my shot. I kept an eye on the first bird before injecting the second in case I screwed up really badly. Second bird got its injection after an hour of observation on the first. Round 2 12:40am - we stayed up late to give the birds their second injection. This round was much easier on everyone involved as I had my wife help by holding them while I gave injections. She held them for a couple minutes afterwards to calm them down. Day 2 - Everyone is alive this morning. None of the other birds are having breathing problems and everyone's eating and drinking. Last night after round 2, I replaced their water/electrolyte/filtered ACV mix with water and organic, unpasteurized, unfiltered ACV. Round 3 10:00am - shots went great! My wife held them again and they didn't even flinch when injected. Round 4: 10:00pm - pretty much the same as the last round. The birds' breathing has returned almost to normal! Now aside from a "sick" sounding chirp, you have to hold them to your ear to hear anything abnormal. Day 3 - Back on a work schedule. Everyone looks good this morning - they're still energetic and appear to be eating and drinking well. Apparently last night was exciting because there's a lot of sand in the water...The little peeps have some bruising around previous shot sites Round 5 7:30am - nothing eventful during shots. Round 6 10:30pm - nothing eventful during shots except I managed to stick my thumb with the syringe while putting the cap on (the needle went through the side of the cap)! Good thing 29-ga is so thin. Day 4 Round 7 7:30am - nothing eventful during shots Round 8 9:30pm - nothing eventful during shots - birds pretty much sound normal at this point Day 5 - The last day; I am looking forward to being done with needles! Round 9 7:30am - nothing eventful during shots Round 10 9:30pm - shots all done, birds all sound good, and I'm happy to be done with poking them (and myself) with needles.