This past year, I used 2-5 year old hens & cocks that were 1-2 years old.Chris - that is what I was thinking ... that once I get a little flock going that is hardy in Vermont - I will use the birds that are older as the parent birds - ensuring they have what it takes in my area .... and then not feeding the medicate starter .... knowing at first I may have a higher loss rate.
What ages do you consider "older" ? I would say for my situation at least living and coming out in good shape from 2 winters ....? but am just forming my ideas on this.
I found I was safe from Marek's past one year -- losses I used have occurred at about point of lay for the pullets and between 7 months and 12 months for cockerels.
I have not used medicated starter for the past 6 years. I also use hens to hatch a good deal of the time too. The hens raise them either out in a pen on the ground or free range outside with them from day one. I have not lost one chick using hens (not even the free range hens & chicks). Chicks hatched and raised inside, also, I rarely have a loss. I keep the brooder as clean as possible and change the water a couple of times per day. Chicks raised outside are healthy, hardy & wise.