 Treating cattle that already have pink eye is going to be a little involved. So primarily because an antibiotic is going to need to be administered and the animal will likely need to have the infected eye covered with a patch. That's unless you can catch it very early. So oxytetracycline antibiotics do work, although resistance in some areas is pretty common, unfortunately. So therefore you will need to have a vet prescribe an antibiotic known to work in your area.