OK, there are a variety of chicken breeds out there, and I am not going to go into detail on specific breeds and characteristics of different breeds. But, we do put "types" on the different birds we sell, so I wanted to give a little lesson on what it means to the meat consumer.
Cornish Rock Cross
The most common meat chicken is the Cornish Rock Cross. This is a bird that has spent decades being cross-bred to select for fast growth. They are a hybrid of a White Rock and a Cornish. The White Rock brings the white feathers and pale skin, the light colored feet. The Cornish brings the size.
It's a little more complicated than that. The two strains of birds have to be selected to produce the best of the bigger breeds. We don't breed our own, because we'd have to feed a flock of females and a few roos that consistently give us these big hybrids, and we frankly just don't have time to be chicken geneticists. A common misconception is that these birds are "genetically modified". No, the DNA is not edited in a lab. This is pure hybridization, and it's happened over generations and decades to bring us these big birds.
We've had several customers this year pick up some chicks at their local feed store, to end up with this huge 8-9 lb birds they thought would be egg layers. Some key things to notice, especially if you have mixed birds - by the end of week one, you'll see these chicks outpace the others in growth dramatically. You'll also see that their hip structure is much farther apart. They need to have wider hips and bigger legs to hold up all that weight. As they get older, you'll see their mobility slow and they don't attempt to perch, where smaller, egg laying breeds surely will. These birds get to full butcher weight in 8-10 weeks. They are pure eating machines, and don't have much of a personality, as they focus solely on food. This is what you find in the grocery store, raised by the 10's of thousands in large structures for the poultry industry. We also raise these birds, but after 3 weeks in the brooder, they get to go outside, in our garden or orchard to enjoy sunshine, grass and an occasional rain storm.
Rangers are another hybrid meat bird. Depending on the hatchery, as they all have their own formula, they may have different names: Red Broilers, Black Broilers, Rainbow Rangers, Red Rangers, Pioneers, etc. Credit is often given to the French for pioneering this more mobile, but large breed of chicken for meat production. We raise these, too. They say they take 12-14 weeks to get to size, we see more like 16 weeks. They are more mobile, still don't have the tendency to perch, are certainly nicer to look at.
They will grow larger than almost all standard chicken breeds. If raised for meat, they won't make it to maturity to be bred for replacements, but it's an interesting concept for us to consider. We've had mixed luck with these birds, as they do not tend to get to the same size as the Cornish Cross. But we raise them due to sentiment that the fast growing Cornish Cross birds are not "natural". The taste, however, is no different.
Heritage are just your standard chicken breeds. Not all chicken breeds are alike, from bantams, that are mini-chickens that lay mini-eggs, to your average White Leghorn (the best of the laying breeds) to fancy frizzles and fuzzy-footed birds. We raise Speckled Sussex and Rhode Island Reds on our farm. The extra roosters get to grow to a decent size and then get butchered for meat. The spent hens also get butchered for meat. Even a giant breed, like the Jersey, can't really compare to a Cornish Rock in size. Some of the roosters can still get to 3 to 4 pounds, tops, but it takes them 6 months or more to do so. Most hens are 3 pounds or less. Most of the fancy breeds weigh even less, and bantams are hardly worth it at 1 pound give or take a few ounces. Not very economical for a meat producer to spend half a year waiting on meat products. These guys will perch, they will also become sexually mature, and if you have too many roosters, that can start to cause aggression.
Since they take so long to grow to size, their meat is tougher. Not so great on the barbecue, but they have much more flavor. They make great soup stocks, stews, braises and smokers. They require a longer, slower, moister cooking method, to help break down the meat and make it softer and more enjoyable to chew. But it's still great meat!
So, what's the point?
The point is that everyone has their own tastes. If you want a good, large, tasty bird, the Cornish Rock is just that. If you still want that big bird, but are concerned about a bird growing SO fast, that it isn't fair to them - the rangers are a nice option. If you prefer that your birds are natural, can breed true, and live a full life, than the heritage breed might be for you.