I was only told not to inject into muscle on small birds. Ive just done it that way ever since, Well that and the only birds i really ever have to treat are the goofy bantys. they always getting the sniffles... then they get better and stay out in the rain again. I had 2 turkey hens sneezing about a month ago. was due to treat with duramycin anyways and 2 days later they were fine. Guessing something environmental messed with emI've never read that Tylan 50 shouldn't be injected in a muscle. That's exactly where I do inject it the rare times I've used it.