I've never had any disease related issues with my birds for 4 1/2 years that I had them. They were from a breeder that I hatched and started a flock. Plus I bought a different breed from another breeder with no disease related issues.
So I'm guessing it might be the way you care for them. There's daily maintenance involved keeping them healthy and making sure they don't get exposed to potential hazards in the backyard.
So I'm guessing it might be the way you care for them. There's daily maintenance involved keeping them healthy and making sure they don't get exposed to potential hazards in the backyard.