Hi! I'll give a quick back story. We purchased 7 pullets from a breeder last winter. Two of them got sick immediately and were quarantined. I'm pretty sure they had/have MG, but by the time we figured all of this out (being new to chickens) my 3 and 5 yo daughters had fallen in love with these chickens like they had hatched them out of their own eggs. Everyone was given a round of Tylan and we decided to keep a closed flock and just deal with it. In the last year two have died of illness, two from predators and the last three are seemingly healthy and have never shown signs of being ill. They all free range. This past spring I may have possibly purchased a few fluffy chicks at the Tractor Supply. Oops. (they're just so cute!) I have been able to keep two separate flocks going for the last 6 months and it's been fine, albeit annoying. The younger chickens have never shown illness and have a nice coop and run but do not free range with the others. (obviously) We had not had any issues with predators at all, but recently the word must have gotten out in the raccoon/hawk/etc. population and it's been all out war on my coops. The old (sick?) chickens live in what we call the Chicken Fortress. It's the product of 6 weeks of work by my engineer husband. The younger (healthy) chickens live in a safe coop but the run needs serious work to keep out the likes of what's been attacking RIGHT at dusk (those mothers!). Question is. Do I marry the flocks, hope for the best (that the younger chickens don't pick up MG from the older chickens that may or may not be carrying it), and keep them all in the Fortress? Or do I reinforce the other run and continue to keep two flocks separate (annoying but probably safer for healthy chickens)? In addition, I have never really practiced good biosecurity with the "healthy" flock. They interact between the fence, I walk in and out of the coops without changing shoes, etc. So maybe healthy chickens already would have picked up MG if it were a problem? I'd LOVE to simplify and marry the two flocks. But I don't want to risk the health of the seemingly "healthy" bunch. Thoughts?