I can tell you from experience that it's tough to raise the CX on a soy free feed and I'd imagine taking out the corn makes it even harder. I've been trying for 2 years to accomplish it, and have yet to be successful. I've been in your position and fixed it by resorting back to a soy/corn based feed. You won't see much difference in growth rate between an 18% to 22% feed. As a matter of fact, I'd suggest using the 18%. I'm guessing these birds are very lean right now seeing as your feed only has 2% fat(it needs to be closer to 8%). The 18% will put some intramuscular fat making them juicier when cooked. After the switch, you will notice them growing immediately. So the good news is you can salvage this batch, but it will take 4-5 weeks to get them up to butcher weight.
I admire and think I know your reasoning for going with this type of feed. Unfortunately the Cornish doesn't do well on this regimate. It's like trying to put 87 octane fuel in a top fuel funny car. There are soy free/non GMO feeds that work almost as good as soy based, but it's very expensive and hard to find the ingredients. The studies I've seen reveal the Cornish still gets outperformed by slower growing breeds on soy free feed. To be honest, I have given up on it. I am going to switch to organic feed and be done with it. I can buy the ingredients and make organic feed cheaper than soy free, and I will have much better results, I'm sure. I did a batch of Freedom Rangers on soy free last year. They got to weight, but it took 14 weeks and the meat was really dry. They also ate almost 30 pounds of feed each which was not cost effective. I figure even if the CX's have to eat a little more organic feed to get to weight, I'll still be money ahead. With the organic feed, I am still avoiding GMOs, so that's most of the battle won.
Goodluck!
Are those Buckeyes or RIR in the picture?
