True, it has to be used quickly once mixed.
It is administered though subcutaneously (under the skin) with a hypodermic needle and syringe in the back of the neck.🙂
I vaccinate all my chicks against Marek's disease. I have used Jeffers Pet and Valley Vet for the Mareks vaccine. The birds need to be 1-2 days old and not have been exposed to other birds or have been outside. So you basically need to have hatched them yourself. I have vaccinated birds as old...