Number one, the birds do not necessarily develop resistance, just as if you were given a course of antibiotics you would not necessarily end up with a resistant pathogen at the end of that. We don't necessarily have to go to stronger and stronger drugs.
There are prudent-use guidelines among the poultry industry that they have developed to mitigate that risk. So they're very conscientious about that. These are their only tools as producers. So veterinarians and producers have developed protocols to avoid that very situation.