I have a large Embden who is between 30-40 lbs. For some odd reason the joint on his/her foot swelled up. No visual injury. It's the joint where all arms of the toes come together. He/she is eating fine and is secluded from the flock, but can see them. Trying to keep him/her from stressing it more. Can I give a 3-4CC injection of Penicillin in the leg muscle? Thanks!