Sounds like a plan to separate s/he if there is no crowing so you can tell eggs.
Another way would be to look at the vent area. A rooster will have the small puckered like a non-laying hen while a laying hen will have an oval "smiley" vent.
If he was compromised by illness, that could explain slower maturity.
However, I hope he is male...he would be the one to breed from if he has survived a Marek's outbreak and grows up into a healthy mature bird. That shows he has resistance. Having the rooster pass that along would be effective for the next generation....more effective than one hen being bred forward.
Vaccines only work so far...they prevent certain strains of Marek's from developing the tumors. The vaccine is considered "leaky" in that it doesn't prevent the disease but only the worst symptoms...and only of the most common strains...like the flu vaccine.
By far the best method is breeding from Marek's resistant stock and limiting your flock's exposure.
An old farmer's trick is to raise some turkeys along with the chickens. Not good for the turkeys as they can gain histomonas or Blackhead (carried by the cecal worms in the chickens and usually doesn't affect the chickens) but good for the chickens as turkeys are magnets for the milder Turkey Marek's which can help protect chickens, when they catch it from the turkeys, from chicken Marek's strains...like Cow Pox was used to inoculate for Small Pox at one time.
Not a perfect solution, but casting a wide net can help. Breed from strong survivors, bring in those vaccinated as chicks (offers some protection), raise a few turkeys.
Let us know if there's a crow or egg.
LofMc
