I would do some research on antibiotics, if I were you. I also haven't had any issues with respiratory diseases in four years WITHOUT administering unnecessary antibiotics. And there is just too much evidence to show that using them when they are NOT needed, reduces their effectiveness when they are. Also, if you are talking about giving just one dose of it twice a year, there is no way it is doing anything at all. Denagard, like most antibiotics, is designed to be administered in a course that runs 7-10 days. A single dose - or a single day of dosing if using it in the water - isn't doing a thing for you.