Walt...........I've raised Chickens and Turkeys togeather for 50 something years now...even in the same pen...with no problems. Like you, I too do not medicate older birds other than Wormer. I am even trying DE to cut down on the amount of that. I truly believe that some of the older Heritage breeds of Turkeys are far superior to some of the newfangeled cross breeds that you see nowdays. They are just stronger and have more vitality than the newer breeds. I occasionally..and not very often...will outcross to Wild birds to regain some of that vigor and vitality. Can you imagine how smart and strong a bird that size has to be to survive on it's own when we have trouble raising them in a pen with good food and water everyday....they are pretty amazing.
I know a lot of people who can raise both turkeys and chickens together, but it doesn't work here. I have tried Bourbon Reds, Royal Palms and heritage Bronze with no luck.
I see these wild turkeys every day and they must keep reproducing.....so they are doing quite well. Maybe I'll catch one and see how long it lasts inside my fence.
Walt