It's the feed.
As riderunner said, Cx are over 60 years removed from the simple dihybrid crossing of Cornish and White Rocks. The industry has selected for larger males (as it is the males who pass on carcass traits NOT the females) and they have also mixed in a couple other breeds along the way. So it is more than just two breeds in their DNA.
Feed is EVERYTHING. When it comes to animals, you get out of it what you put into it.
If you can't do fish, you may not be able to do shellfish. If you can't do shellfish then basically any commercial feed on the market will set you off, because their source of calcium is usually Oyster Shell. OS is known to cause reactions in people who are allergic to shellfish if they eat the eggs or meat from birds fed the supplement.
As riderunner said, Cx are over 60 years removed from the simple dihybrid crossing of Cornish and White Rocks. The industry has selected for larger males (as it is the males who pass on carcass traits NOT the females) and they have also mixed in a couple other breeds along the way. So it is more than just two breeds in their DNA.
Feed is EVERYTHING. When it comes to animals, you get out of it what you put into it.
If you can't do fish, you may not be able to do shellfish. If you can't do shellfish then basically any commercial feed on the market will set you off, because their source of calcium is usually Oyster Shell. OS is known to cause reactions in people who are allergic to shellfish if they eat the eggs or meat from birds fed the supplement.