Slow Growth in CX?

[bigredfeather]

All the CX I have done this year have grown very well. Their average butcher weight has been 4 1/2 pounds at 7 weeks all year........until now. I currently have 2 tractors of birds left. One tractor has 34 birds in it that are 8 weeks old and at best the biggest ones would dress out at 3 pounds. The other has almost 100 that are 6 and 7 weeks old. They look horrible. These birds seemed to be growing according to schedule until the past 2 weeks, then they just seemed to stop. The weather has gotten cooler, but I increased the amount of feed they get per day to compensate, and they have been eating all of it. I have had to postpone butchering the last 2 weeks because the birds weren't ready. I can't figure out what's going on.

Here's what I know isn't the problem:
It's not the chicks. I sold 50 of them out of the shipment to friend of mine. We butchered them this past weekend and they where huge.
It's not coccidiosis. Minimal red colored droppings and no ruffled feathered or lethargic birds.

Potential problems I can think of:
Some type of sickness/disease - Not sure which one if any. All of them appear to be fine. Eating/drinking ususal amounts, energetic(at least as far as a CX goes).
Feed issue - This is the best explanation I can come up with. My mill checked their records and they don't show any errors in the mixing of the batch of feed I'd been feeding, and they have not offered any other possible explanations. I switched to a different feed on Saturday, but so far haven't noticed much growth. Not really enough time to see any noticable growth.

Anybody have any thoughts or other possibilities?

 

[TDM]

Last weekend I processed about twenty 10 week old cornish cross for a customer. They appeared to be malnourished, with carcass weights between 2 1/2 to 4 pounds. There was no fat around the vents. When I cut into the gizzard, it appeared to be a hard tangled lump of fibrous material. When I showed it to the customer, he said it came from one of the polypropylene tarps used to cover the chickens.

 

[TDM]

I first noticed that the crops remained extremely full, which was odd since the birds had been sitting for several hours without food. When I cut into the gizzaed to remove the contents, it didn't just wash away with the stream of water. Instead it stayed one fibrous lump. Basically the bird's gizzard couldn't pass the fibrous material, and there was very little room, if any, for normal digestion.

 

[bigredfeather]

My birds do not have access to any type of material that could cause this. The only thing they can get in their crop is feed and fresh green pasture.

 

[becky3086]

If they are eating all their feed, I'd just plain feed them more. That is all I can think of. Check out what your friend did differently with theirs maybe.

 

[TrinityFarms]

How cold is it getting there? Cold weather can lead to ascites especially in cornish cross. The altitude and sodium levels of the food and water could also influence this, which may be why your friend's birds worked out.