Not at all true. My Cornish rock hens are now 5 months & going strong.
They are also producing 1-2 eggs a day..
Sorry Silkie,
You may have made a typing mistake. It happens to us all sometimes, however, I am sure you will recognize the logic in my next statement.
A "Cornish Rock" Is typically a White Cornish Rooster (Good luck finding of one these to buy, the commercial chicken farmers hold onto to these like gold and I have never seen a hatchery or likewise to have access or sell them), Crossed with a White rock.
A Cornish hen is not a very good layer. You may get one to two egg/week if you are lucky. However, a white plmouthrock hen will produce 160+ a year. It wouldn't be very economical to use the Cornish hens for anything rather the producing more Cornish roosters, or broiling them.
The reason white is the chosen color in the industry is because the pinfeather pigmentation is not present therefore the carcass/skin looks slightly more appealing on the shelf. However, I would put a Dark Cornish/ Barred rock, Dark Cornish/ Sussex. Dark Cornish/Delaware against almost any white Cornish/Rock as table birds.
In regards to the question of breeding the Cornish rock hen....Sorry, I think you will have poor luck. You don't want to get too attached to these little chicks. Their muscle structure grows so much faster then their skeletal system, digestive system, and neurological system. Their breast get so large, they have been known not to have the energy to get up a drink water on a hot day. Its common to find them dead if not butchered between 6-12 weeks from a variety of developmental issues. They are freaks, and great on a rotissori.
Is their any real reason to want to breed them back to a Plymouth rock even if possible? They simply do not have a history of being a long term healthy bird.
If you want to produce a big bird, try a Jersey Giant. We have a rooster who is huge, although I don't know how much he weighs exactly. He is nearly 2x the size of our Barred Rock Roo (Who is not little)!
We are considering breeding our Blue Jersey giant hen to a Dark Cornish just for fun. Could be interesting.