Had a necropsy done on a hen I had to put down recently, it came back that she died from cocci, but also had marek's. My other hens are acting fine, so I've accepted that I will have to have a closed flock now. When I go to replace my layers next year, the new chicks will be exposed to the Marek's. I'm hoping to find out which breeds are most susceptible and which are most resistant to Marek's so I can give the new chickens the best chance. Here's what I've seen so far Most Susceptible: Silkies Sebrights Less Susceptible / More Resistant: Egyptians Fayoumis White Leghorns* [edited on 11/6/15] Any advice on breeds or best practices (maybe buy vaccinated chicks)? *From a random internet comment "For working on susceptibility - some research states that the B21 gene may indicate some resistance. white leghorns are supposedly more resistant than RIRs and since most sexlinks contain RIR genetics, they are some of the ones that have vulnerability. "