1) They think they can't/ don't know how
Since the companies doing it use trained geneticists to breed them and poultry science specialists to efficiently feed them and manage them to keep them alive until butcher size, I believe you are correct. They don't know how. That doesn't even get into keeping the parent and grandparent flocks alive and producing.
2) Most folks can't keep 4 separate breeding flocks just to produce a special crossbred
Most implies some could. Why don't they since the Cornish X is so efficient? There is a market.
Please tell me what will be the process.
Back in the mid 1900's companies developed the first Cornish X meat birds by selective breeding. Two of the parent breeds they used were Cornish and White Rocks, hence the name of Cornish Rock that is sometimes used. It was never a simple cross of Cornish and White Rocks, it took many chicken generations to develop what they wanted. That was a bird that was very efficient on converting feed to meat, had a certain proportion of white meat to dark, and could get to butcher age pretty quickly. The younger they could butcher them the more flocks they could raise each year. In the 1950's this Cornish X pretty much replaced the Delaware, New Hampshire, and certain strains of White Rock as the preferred meat birds. They were just too efficient.
Since then they have continued to improve that bird. They are not so much trying to get it to grow faster, they could do that, but they are on a fine edge of also keeping them alive until butcher. It is not just genetics but how to maximize feed efficiency and how to house and manage them. They want a relatively robust chick that doesn't just die on them.
Several different companies have developed their own strain of these meat birds. They have invested millions into developing them and aren't ready to give that technology away for free. That is a highly guarded industrial secret as you would expect.
The basic model they have developed is that they have four grandparent flocks. Each of these flocks produce one of the grandparents of the birds that will mate to produce the broilers. One of these flocks will produce the grandmother of the father of the birds that will lay the eggs fro the broilers. A separate grandparent flock will produce the mothers of the mothers of the target laying flock.
Then they keep two more flocks. These are chickens hatched by crossing the appropriate grandparent flocks. Then they take the appropriate males and females from these two flocks to make the flock that actually lays the eggs that hatch into the broilers. It's not four flocks, it's seven.
These flocks do not need to be on the same premises, eggs can be shipped to a hatchery and baby chicks can be shipped to whoever is raising that flock. It's not that unusual for farmer to contract to raise one of these parent or grandparent flocks, but there are penalties to keep the technology secret. Also, these flocks have the genetics that make them grow fast. The people raising them have to manage them and feed them in a way that they don't get so big that they can't mate, let alone fall over dead. They have to balance how much to feed them to keep them healthy and laying eggs without overfeeding them to the point they die. An example of how they are refining genetics to help with the entire process, they have learned to use dwarfism in some of these flocks to stop them from growing so fast yet keep the dwarfism out of the final product.
Perhaps you can see why I'm skeptical of someone achieving consistent results with this in their backyard. Consistent results, not an occasional freak.
@Danish aseels several people on this forum have tried to breed their Cornish X chickens to produce a meat bird. It is a hybrid cross so results will not be consistent and generally not to the standards of the Cornish X chicks. But they still have excellent meat qualities compared to dual purpose birds. Most that try that are disappointed though because it is so hard to keep the breeding birds alive. They grow so fast and get so big.
Some people on this forum try to cross a Cornish X (or Ranger) with a dual purpose breed to get a pretty good meat bird that is easier to keep alive. These crosses certainly do not measure up to the standards of the Cornish X but they can get some pretty good meat birds from them. There are few of those threads on this forum.
Bottom line is that you will need to continue buying the chicks if you want Cornish X chicks. To me it is unrealistic to think you can breed them yourself. You are quite welcome to try but remember a big part of it is not just genetics, it's managing then in a way to keep them alive and productive laying eggs.
Good luck!
