Thankyou all for your replies. I am aware of the abundant studies on CX birds in confined trough feeding situations. This is why I said my situation is so different - I doubt those studies can mean anything for me. Mine are not CX, they are red broilers (K22's and Freedon Rangers) they forage...
A neighbor I respect, who's raised meat chickens for 30 years, said she butchers when they start putting on fat - because she believes at a certain stage they switch from meat production to fat production. I'd like more than hearsay on this important topic - I want to raise large broilers - but...