I'm no expert on Cornish X. I've just raised them for meat and then . . . there was another time that I hate to admit to
. . . but it was all my brother's fault
.
He decided to keep 7 CX hens - - then he gave them to me. I kept them awhile - - then gave them back. This was long ago and I honestly think that the CX in the 1970s had a much better chance of survival to adulthood than they have now.
Raising broiler breeders has everything to do with feed restriction. Feed is allocated very carefully because these birds will
eat themselves to death.
Broiler breeders are the parents of the birds you have. Limiting the amount of feed to these birds gives them their only chance to reach maturity. But, you need to separate those birds you want to keep and begin at just a few weeks to control how much food they eat. May as well get a feed scale AND a scale to hang in the coop to weigh the birds. It is that critical.
Or, I understand that some people keep these birds
without feeding them at all!! They are allowed the run of the farm and either they run . . . or forage, or they don't eat.
Here are a couple links to the commercial (expert) approach:
Alberta Ag Agency
University of Georgia
Hope this helps but you may want to step back, and try a different route. Buy the heritage breeds that were once used to produce these heavy meat birds and breed them. Folks over on the Meat Birds ETC forum often talk about their experiences with this.
Steve