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- #21
I thought it was barred PlymouthTo make CornishX (also called Cornish Cross, or Rock Cornish Cross, or other variations of those names):
Originally, decades ago, White Plymouth Rock hens bred with White Cornish roosters.
The hybrid chicks grew fast and had big breasts (as compared with other chickens available at the time.)
Of course people tried various other combinations of breeds, and started selectively breeding for the traits they wanted in the chicks.
By now, there special lines of parent stock (that you can't buy anywhere). Two lines are crossed to get hens who lay lots of eggs (so they can hatch lots of chicks) and grow pretty well. Two other lines are crossed to get the right roosters to breed with those hens. Roosters don't have to lay eggs, so the rooster line would be selected especially strongly for fast growth and lots of meat.
The Cornish Cross chicks they produce will grow fast, to a large size, but they have health problems if you try to raise them past about 8 weeks of age. Their parents would have the same health problems, except that they are raised on very limited feed (semi-starved to stunt their growth, so they are closer to normal chicken size instead of enormous balls of meat.)
If you repeat the original cross of White Rock x purebred Cornish, you will find that they grow much slower and are much smaller than the modern Cornish Cross. So the name stuck, but none of the parent types would match any recognized breed of chicken.