Crowderfarms, I picked up a bag of minerals that has chlortetracycline as one of the ingredients. I mainly picked it up for helping reduce the chances of pink eye. I have vaccinated for it, but that isn't always fool-proof. The flies seem to be bionic this year,the rubs and sprays slow them down, but not completely. I read where this medication has so many uses. They use it for pink eye, scours, respiratory problems, foot rot, anaplasmosis, etc.... It reminds me of the tonics the traveling men sold many years ago for all ailments. I have read where it is used to medicate calves, but on the label of the bag, it says, "For weaned beef cattle." That threw me a little. The dosage is 1120 mg per pound. Now I know it means that they have not tested calves for the withdrawal period before slaughter. I knew if this had been a problem at one time, that someone here would know.