Doxycycline hydrochloride (sometimes called doxycycline hyclate) is a tetracycline-class antibiotic, and if you work with pigs or poultry, you probably reach for it more often than you realize. Compared to oxytetracycline, its older relative in the same family, doxycycline is 2 to 10 times more active against bacteria. That is a meaningful jump, especially when you are dealing with mixed respiratory infections where mycoplasma and bacteria show up together. Roughly speaking, doxycycline covers bacterial infections, four types of “body” pathogens (mycoplasma, chlamydia, spirochetes, rickettsia), and one blood parasite. That breadth of coverage explains why it shows up in so many treatment protocols. Where It Actually Gets Used Bacterial Respiratory Infections…