My pet duck is 12 years old. Very old for a duck. My pet pig who is also very old snapped at the ducks leg. The pig has no teeth left, so there is no open wound. But, I am pretty sure the pig caused some damage under the skin. It has been a few weeks and the duck limps a bit, is not eating much and is not nearly as active. I don't really want to take the duck to the vet, as I fear the stress of the trip my kill him. Can anyone suggest an antibiotic I can buy online or at a feed store that may help?