No, not on antibiotics, would not know where to get them, and I have read not to use them as it kills off the good bugs in the gut. I have given them the probiotics in several ways...in water, plain yogurt (they love it), and sprinkled on food. Two hens had it, the one that didn't have it too bad is cured and back to laying eggs. The Welsummer just won't give it up, though. We have been washing her butt, setting her in a tub of epsom salts water, to clean off the gunk, and spraying the area with anti-fungal, and it's gotten better, but won't go away completely. I am getting tired of butt-washing every day, lol. What was the saying my kids used to say when they were little that made them laugh. Oh, it was ... Guess what...chicken butt.