We raised some Jumbo Cornish Cross for meat, and they seem to die a LOT easier than if I would of got something that was a little slower growing like straight Cornish. When they cross with the Rock or other meat bird, they put extra weight on shorter legs, and they sometimes have leg failure, but we had 4 out of ten die of heart attacks (Flat on their backs, wings spread). Do a google search for sudden death cornish cross. I passed this info by my uncle-in-law that has raised/judged poultry for over 50 years. He said he has had the same problems with the crosses every time he tries it. He now raises Silver Laced Wyandottes, and Buff Orpingtons and lets the hens hatch out whatever amount, and then eats the extra cockerals and hens that have quit laying, and lets the pullets replace them. Takes a bit longer but you end up with more meat for your money. Pick out 25 or 50 straight run Buff Orps or SLW and you have both covered, at a better price!