Last time I used penicillin was for a vile retained placenta and the vet gave the initial dose then instructed me to re-treat every other day at twice the labeled recommendation. The cow pulled through, bred back & was fine, but seems like an excessive amount of shots when there are so many other options. That said, it was probably 9 years ago, that particular vet is now semi retired, and the other 2 vets that focus primarily on large animals have never treated with or suggested penicillin (at least for my herd). My last bottle expired. What would you use it for?