With regard to Marek's vaccination, I think it depends on where you are in the breeding programs and how many extra birds you are willing to keep "just in case." I keep small matings of each variety (12 this year), so I vaccinate chicks as they are hatched right out of the incubator. The later chicks hatched under hens, I don't bother to vaccinate because they have already been potentially exposed by the setting hen, but that is a small minority. I have been vaccinating for Laryngo just because it is such a deadly disease, and there is no way to breed for immunity to it. And then I vaccinate for Newcastle/Bronchitis just as an "abundance of caution." All these vaccines are relatively inexpensive and easy to administer. Mycoplasma vaccine is expensive, and I chose to breed for resistance. It does not seem to be a killer unless it is combined with some other disease such as Coryza, Bronchitis, etc. And that seems to be working for me, as I can't remember the last time I lost a bird to Mycoplasma Gallisepticum alone.