Great thread, fantastic comments! I have been growing out cobb 500 for about 7 years in an urban homestead environment. They have been the primary source of meat for my family of 4. I’ve grown out about 300+ so far. You can not beat the production of CX and you can’t beat the liveliness of the cobb 500 strain. In many ways, if done rite, this bird is a thoroughbred, a spectacular (as someone said). “supersonic” bird.
Trying to grow them out to breed seems pretty futile. You’d be better off adjusting the cross upstream before the CX. Zillions of people have tried what you are doing, it’s a neat experiment, and I wish you luck, and every time I read about these adventures I learn something new but always come away with an even deeper respect for what this cross achieves. I can make a strong argument that your better off learning to work with its ways rather than trying to change its ways.
2.5 lbs of grain to a pound of meat with dressed weight of 3-5 lbs at 6-7 weeks and dressed weight of upwards of 9 lbs at 9 weeks is bonkers amazing. It’s the big agro industrial farms where the real nightmares happen. The small backyard grower has the opportunity to fine tune their practices and create a humane environment. From an environmental impact perspective, they provide the lowest carbon footprint of any meat producer, better than rabbits and of course way better than beef (which is more like 18 lbs of grain for a lb of meat).
I have no issue with folks who are curious, trying to tweak the genes, but it’s very unlikely to pan out. There are already slower growing meat birds for this purpose. The minute you breed a cross, just like with plants, you end up getting a smattering of its predecessors in rather prescribed proportions, than can all bee worked out in a punit square, what geneticists use to illustrate how a cross works. You will not get a pure and sustainable stock. Each time you breed the proportions of birds that represent the predecessors will be different, and depending on which ones you breed in the next generation, you’ll get entirely different genes. It’s a pretty handy phenomenon if you want to charge money for chicks that prevent people from replicating the breed itself. I’d say it’s part of some diabolical plan for world dominance but the fact is, nothing beats this cross, hands down, so I gladly pay for a breeder to supply me with the outcome of all their work.
IMHO your time would be better spent either trying out the many other dual purpose birds or slow growing meat birds or, mastering the care regimen that leads to the CX remaining happy and healthy and award winning productive. Restricting food is torture for them, an absolutely miserable state. They have 10 times the metabolism of virtually every other chicken strain. They live fast and die young, waking up with an aching pit of hunger in their belly and able to process food about as fast as they can get it in their mouths. The marvel of this, when combined with good practices is truly something to behold. To top it off they actually have an incredibly sweet demeanor if you get to know them.
The key is applying principles of humane husbandry. Avoiding heat lamps, the light keeps them up and eating to the point where their muscles outgrow their joints. In warm months they need no heat at all (60f+ at night). The rest of the time they need a radiant heat source at the most, then wheened off completely as soon as old enough to generate the required heat. the lack of light at night makes them sleep and eliminates the need to remove the food, they self regulate and grow stronger bones with less leg problems just by eliminating the light… their bones keep up with the pace of muscle growth, at least more so. Moving water further from food and raising both to encourage them to stand as much as possible is very helpful. At week 5-7 they will begin sitting due to their weight, this is normal. They have lived a full life by the time they are 6-8 weeks old and from there, they decline and typically succumb to heart issues. (I can’t help hearing the jingle of jimmy buffets “living and dying in 3/4 time”, except these birds express their entire genetic capacity in 1/10th the time)
A deep litter is key to moisture control, a high protein diet means wet poop, with lots of amonia if let sit. Deep litter leads to a dryer bed, eliminating foot sores, and allowing them to have a decently clean, white coat. They will remain energetic and frolic up to about 5 weeks.
The food is very, very important. I just tried a new ration and it failed miserably. I reached back to my supplier and they explained some of the science behind this thoroughbred’s nutritional needs and it’s not just protein content. They have a specific amino acid profile they need to maintain for their heart to be able to keep up with their mind boggling growth.
Anyways, good luck, have fun, be humane and keep us updated on what you learn.