I am using non-medicated feed right now and had no problems...but it is my first time using it. There have never been any chickens on the property. I change the water 2x a day, change the bedding every day, sanitize the feeders and waterers once a week, and clean the brooder every 3 weeks...so I really dont have any reason to use medicated feed. I chose the non-medicated feed because I wanted to be organic but I vaccinated the chicks for marreks disease...so I guess thats not really organic...right?